1) Any amount of force does not kill him.
2) Not amount of heat or cold can kill him.
3) He will not take in any liquid however if you explode a syringe he will be affected but not killed.
4) Attempting to rip off a body part results in him just bleeding everywhere.
5) He is immune to things that would delete him.
6) He can not be drowned.
7) He can not be burned.
8) He can not be electrocuted.
9) Reactor explosion does not work.
10) Dropping him into the void does not seem to work however you can't find his body, and it might be cheating.

so i insta killed him with rush b p90 from another orv mod

he still stood up tho

number 2 kinda lied, i killed him with using frozen acid water

pretty sure this doesn't count but the New Prison Realm Mod couldn't contain him