If you have a flyer then you should go a small distance of the Rex shoot it with your trancs get on your flyer and repeat. Once you have it knocked you are going to want to remember where it is, kill a Dino that gives prime meat like a bronto or a allo wait till its hunger is very low give it the prime meat. Ps bring lots of narcotics.

Here's 2 ways to tame the best choice for boss fights:

1) The smart way

Build a 2x2 space with 8 stone fence foundations and build up 3 high with stone doorframes. Place 2, 2 high pillars next to each other in front of one side so you can support wooden ramps with them which will go from the top of the wall to the ground. Lead your rex of choice inside and shoot it with tranq arrows or darts if you're rich and have an increased longneck. Feed it prime meat but note that you will need kibble for it not to lose any levels if it is a 130+ and you're playing on 1x taming.

Note: place the trap in a spot without a lot of spawns as to not block them

2) The hard way (not really)

If you have a really good raptor or sabertooth you can safely knock out a rex by spinning around it and shooting. Do note you need a decent amount of competency with shooting while piloting a creature, but it is my method of choice nowadays. Once it's knocked out just leave it there with some prime meat and replace the meat every 15 minutes so it doesn't spoil.

Note 2: Most dinos will not attack wild carnivores unless provoked, rexes are in the group that doesn't get attacked so you don't need to worry about them dying while unconscious

(Ark Survival Ascended) If you sprint and jump to the left as a Rex is about to bite you, it will miss. Continue walking left, circling the Rex's right leg and the Rex will be unable to hit you. Make sure to stay a small distance away from the Rex's leg or you will take stomp damage. This can be used to tranq a Rex and tame it without a trap or flying mount. (Tested with 115% speed)

So here's how I tamed my rex, 1:you kinda gotta have a flying dino a tapejara is VERY RECOMMENDED I used one too tame my rex so anyway since the tapejara's saddle has 3 seats you could bring a friend to ride on the back 2:craft a crossbow (recommended) and some tranq arrows will do (87 or more or less), But you must be a very skilled ark player to use a normal bow to knock a rex out as normal bows have low durability and power but do, um sort of alot of tranq damage so I prefer bringing a crossbow, you will knock a lvl 2 rex out VERY EASY with maybe say, about 57 or more tranq arrows and you don't really need that much narcotics for a lvl 2,(these are just tips for lvl 2 rex taming anyways) 3:drop your crossbow and tranq arrows for your friend (or if your playing on Xbox and playing couch co-op give it to your couch co-op freind) make sure your freind is on the BACK seat of the tapejara saddle, OH! And bring Alot of narcotics if your planning on taming a high level rex, (to make narcotics craft a mortar and pestle get as much spoiled meat as you can(and narco berry's) then put them in the mortar and pestle and don't forget to unlock the engram "narcotics" then craft as much as you can (end of narcotic introduction) 3: okay your almost ready to tame a rex 👍 then gather ALOT of meat, then you and your partner should fly too (locations of rexes: mountain's RARELY, the best place of all is "carno island" you should look on your map and see a big island just this way ↗️ up on your map radius go there, carno island is VERY DANGEROUS though because of sabertooths, carnos, alpha carnos, (argentavis's, aka giant hawks) and alot! Of rexes then fly there on your tapejara with your tribe member, you should fly close and above a rex to get it's attention(agro) then THIS IS WHERE YOUR TRIBE MEMBER MUST START firing the tranq arrows at the rex (most likely to shoot it's face, keep flying over it and your tribe member shooting down at it until it starts to flee, the person riding (controlling the tapejara) must fly after the rex as fast as you can! AND YOU BETTER HAVE BROUGHT ENOUGH TRANQ ARROWS TO KNOCK IT, (TIP you must know:face the back of the tapejara at the rex your tribe member is firing at so your tribe member can get a wayyy better shot at the rex)4:if you chase down the rex and your tribe member keeps winging it, will those 87 arrows or more the rex should eventually drop, depending on the level of it, a lvl 2 rex doesn't take that much arrows but bring Alot just in case anyways when the rex drops put your narcotics in it's inventory (and raw meat) then your good to go if it's torpor (the purple bar\knockout bar (how long it's asleep, only seeable while close to the unconscious animal.) Is depleting or almost fully depleted you should feed it the narcotics that are in it's inventory (RT, to feed sorry idk what button it is on Computer\PC) it will automatically feed and tame on it's own but force feeding it will not work and fill the taming bar, so just leave it for a bit or protect your unconscious rex and wait until it's fully tamed and yours and keep an eye on that torpor! 5:if you successfully tame it you now have a killer beast in your hands if you already crafted a saddle for the rex you can then kill everything in your path but if not go craft one,( it is does require kind of alot of ingredients to craft a rex saddle here are the requirements (380 hide,200 fiber,50 metal ingot) well that is the full tutorial on how I tamed my rex his name is Ray he's a lengthy lvl 84 welp I hope this helped bye 👋.

Look

1 petrandon

And 1 soothing balm

And 1 primal meat

And a bow with 10 Tranq arrow

Let your petrandon have a battle with him or her and you can shoot the arrows from a far

When he's or her get knocked

Whilst you're petrandon for passive

And then tame it with soothing balm and 1 primal meat

Easy!!!!!!!

I'm in level 53 and I have 2 spino and 4 rexes!

Good luck

Just tried taming a Rex. I brought a bit more tranqs than the taming calculator told me too. I hit the Rex with every shot and low and behold. Not even half torpor done. The calculator has been off for me before but not by this much. Just letting you know so you don't almost die like I did :)

First get a ascendant rifle then load it with 200+ tranq darts the. When it’s knocked out put spikes around it (wouldn’t recommend metal as it uses too much metal ingots) then go to the south zone 2 cave and get the artifact and then tribute it for a soothing balm then after that feed the red then go to sleep then when you wake up get your Dino and kill a low lvl stego nearby for prime meat and feed it to the Rex

Want a op Dino here

Step one find a Rex

Step two knock it out woth tranq dart or arrows and surround it with fences

Step three give it prime or reguler meat and bring naracotics

Step 4 if you want to tame a really high level bring soothing balm

Step 5 get a saddle for it

And boom tamed

How to tame a Rex

Step 1 find a Rex

Step 2 bring tranq darts or tranq arrows whatever you prefer

Step 3 bring naracotics

Step 4 knock it out

Step 5 give it prime or reguler if you have no prime

Step 6 wait for it to tame and surround it with wooden spike walls to be safe

And boom the Rex should be tamed oh and when you find it probably make a trap these guys are strong

How to tame a Rex.

1-you can outrun it eazily by using a raptor or a flying mount while keeping ahead of it and getting off and pelting it with tranq ammo of your choice,use dinosaurs that yih can use your tools and weapons on its back,a raptor or any others could work,even without a fast tame,you can outrun it with 120+-130 movement speed.

the second method is:

2-using a trap for the Rex,a trap that's wooden will work,but it's risky as if you use it on a high level Rex it will break the wood very eazily,I reccomend a stone trap,as it cannot damage stone structures,the trap that's 2 walls high and 3 walls in widgh should work,attract it's attention and lure it in into the trap and outrun it,once it's in the trap,pelt it with tranq ammo until it's knocked out,keep it asleep(it's torpor goes down quite slowly,but it has alot of torpor so bring alot of tranq ammo)use narcotics or biotoxin,use a soothing balm for high levels and in ark mobile also use a soothing balm,use raw prime meat or raw meat,for a high level I reccomend you use it's preferred choice of kibble,which is the quetzal kibble.

3-you've now got a Rex!now I will tell you it's advantages and disadvantages.

Advantages:it's base damage is 75(level1),and has a big hitbox when attacking,also it's hitbox is pretty big like I said,so you can land extra hits when a Dino is trying to get to you.

Disadvantages:it has poor stamina,slow swim speed,and kinda slow movement speed that's close to a raptors.

Fun fact:it's saddle is unlocked at level 74.

If you want to tame a Rex you have come to the right person

Prepare:

•Stack of 50 knockout ammo (tranq darts or tranq arrows)

•Weapon (crossbow, bow, rifle)PS: make sure your weapon is at full durability!

•Taming food (I recommend the pulminoscorpus kibble but any meat will do)

•A LOT of Bio toxin or narcotics(I don’t recommend narcoberries)

•I recommend to bring a strong saddled tame that is tall enough so raptors can’t get you ( they are a challenge without a mount)

Knockout:

There are two methods of knockout

Method 1: TRAP

First grab 9 to 16 large bear traps and arrange them as shown:

@@@. @@@@

@@@ or @@@@

@@@. @@@@

And grab a flying mount (I recommend pteranodon or tapejera)and get the Rex to agro on you and follow you and run him into the bear traps and fire away. Feed him the food and voila you have a Rex

Method 2: THE CHEAP AND EASY

This is a much easier method than method 1 but it can be dangerous

So find a cliff that is tall enough so the Rex can’t reach you and fire away(be careful because if you fall off the cliff you can kiss your entire ark legacy goodbye)

And either way works but they require different skill sets. And make sure you feed the Rex the bio toxin constantly and you have yourself the ultimate boss fighter!