necron cryptek (of any kind of your choosing) x DC young justice (this will answer the question of how much damage and one of these guys really do with almost nothing stopping them) 

male psyker x bleach ( the same thing I said for the young justice idea he will not be that ummmmmmm insane I should put beck the warp will be calm and plus a psyker soul reaper would be pretty nutty like would would his zanbato and banki be like)

salamander space marine x fallout new vages (YES omg how has no one has dome this before is soo good)

male inquisitor x Castlevania ( honestly its a good one to see what to do with)

imperial knight house x  tenchi muyo! war on geminar ( that is the only mecha anime that can work with this sorry 😅😅😅)

tech priest x marvel( i got nothing to say just a random thought)

enjoy these ideas if you are going to use them, make sure to  "@" me, and message me so i can see what you do with it because I want to see you creative 😉 😘. have fun 👋👋