He is definitely not a defender that's for sure. The only thing you have to worry about is his pseudo recoil effect that goes away after a few seconds, and even then its not a death sentence to ignore it and keep hitting him. Literally any champ will do, more damage the better I guess, because utility is not necessary.
I used starlord to get his health down fast but if I somehow lost I then used gwenpool because her bleed gives him power gain which is exactly what I wanted so I could keep baiting sp2s instead of sp1s and then I would use her 3rd for the armour break but if I somehow lost with her I used hulk and hit him on purpose to take that armour damage back at my own health allowing me to take advantage of hulks strengh increasing. You just want someone who can dish out loads of damage really.
I used 5/50 Blade. Get to your L1, throw it, tap a few more hits if you need to in order to get him to his L2, then back up and evade his attack. Rinse, repeat. Though, I have only got him down to 2%. Never got the 1 shot.
Comments
The immune mini-boss node disagrees.
Good luck..