In alpha phase, you must clearly use level rex type dino over 350 with full tek pick up the keys and if you are not solo, be several in tek tier to fight it, you will have a great chance to win if you organize well.
So I found that tame a male x Rex level 150 and a female level 150 then breed and get it to 100k health and then pump damage bring a shotgun a yuty 500 shotgun shells for gamma and have a bunch of speed I had a Rex that did 20k per hit
Attacks: Laser beams, and can summon corrupted Dino Tars and corrupted avatars (high levels!!)
To fight this boss, there are 2 ways, and here there are: First army: A lot of tek rexes, a couple yuties, and a lot of daeodons. Second army: a lot of tek/ or normal gigas, a couple yuties, and a lot of daeodons. Good luck!!
This is the hardest boss in the entire game, even on gamma he makes the alpha overseer look like a chump, if you somehow manage to beat him. All your tamed Dino’s that you bring will teleport back to wear you originally teleported from, don’t use rhinos to charge him since he floats in the air, and you only have a mere 15 minutes to kill him