It's best to leave them alone unless you want to tame them. They act like spike walls, so you and your dino take damage when you melee it, and it's a lot of damage, even low level ones do a lot. If you want to kill one, it's best to use ranged attacks like a gun or a wyvern blast.
While battling a lone kentrosaurus or even a herd it is highly advised to use ranged weapons. Due to the kentrosaur’s slow movement speed and ability to reflect moderate melee damage using hand held weapons and attacks with smaller dinos can cause serious destruction to you and your tames.
Woah look a kentrosaurus. I think I'm going to tame it. (Shoots it) ohh shit it's grabing me. (1 minute later) its taming so slow. Once it's tamed I go into forest and find another one. Hey Brady look, another one. ( 1 second later) ohh come on I didn't even shoot you this time.
If one of these things are hiding in a bush and you can't see it and you pass it dude it's annoying because if you walk past it do you think its a peaceful creature right do you walk up to it like hi and he will pick up your mount and toss it around like it's a ragdoll and it will pick you up after it kills your mount and federal you around like a ragdoll and kill you and when you go back you can get thrown around again and again and again and again they are annoying but good for battle though I would recommend you to stay away from these guys unless your high enough level to tame it but otherwise stay away From it warning warning warning danger danger danger