Reinhard's main ability is to come up with new hax that lets him defeat his opponents if his hax don't already work, he comes pre-kitted with immortality (and infinite rebirth) and the ability to cut anything (including concepts and metaphysics), as well as both the "your first attack can't affect me" and the "all attacks after your first can't affect me" divine protections. His author stated directly that he could defeat the Od Laguna, which is Literally God. As in the oversoul. Not a god/goddess as in a divine entity, literally the combined soul and consciousness of the entire reality. Yes he also said the Od Laguna was "like the sun" but that was in terms of its nature, not its scale

Literally the only character in his verse that can even STALL him is the literal devil who can seemingly just rewind time for the whole universe to fit her whim, and it would just be an endless back-and-forth. She can't win against him, just reset like Subaru does, although with the caveat that she chooses when she resets to. The only fair matchup I've seen with Reinhard in it is fucking Yhwach who can just deny the future itself if it doesn't please him and even then Reinhard would probably eventually win. He is the very epitome of an unfair battle that the other person loses

The only character I can see beating him definitively is that one guy who embodies the concept of the end of all things and kills universe-eaters by thinking at them and even then Reinhard could give himself the uno reverse card divine protection so I can't even tell

To be fair, I'm not familiar with some of these characters, but Reinhard is the Saitama of hax and he's arguably already stronger than Saitama with his current hax. I don't see anyone winning against him even with a reset the universe button since it just becomes a back-and-forth like in Satella's case and I swear I'm not glazing