who would win.

Cracker one piece

or

Reiner  from AOT

So cracker and reiner would be in a way evenly matched.

like cracker has a protective armor to trick the opponent into thinking he's dead which would catch reiner off guard,till Cracker comes out and,well if reiner sees cracker coming out.

he'll have a problem like just because he's a titan doesn't mean he'll be vulnerable to the nap crackers sword can cut that.

so if cracker,actually sent 1000 warriors  and,Goes to the nape than he'll beable to cut it and kill reiner.

now how can reiner win.

well if Reiner uses enough force to knock cracker out or is near an ocean then he'll gain a win.

cause the win Reiner needs to gain is to either knock cracker out or Throw him into the ocean.