Demonbane

Demonbane is a Lovecraft-inspired mecha series that started out as an adult visual novel from the developer Nitro+ and has various spin-offs, novel adaptions and even an anime series. Despite it throwing around names of Lovecraftian beings around, it has little to do with the actual mythos and is more of a homage. Demonbane is by far the most absurdly, stupidly overpowered mecha in all of fiction, it is so overpowered that Demonbane doesn't even follow logic. It takes on various forms and upgrades in the series and one of the upgrades is the War God Demonbane which is so massive that it shatters an universe because the universe can't contain it and its final form, the Elder God Demonbane is so hilariously overpowered that just it moving was creating and destroying multiverses and it can even beat omnipotents, so in other words, it is beyond the concept of infinite power. This version of it is apparently beyond omnipotence. It can also summon infinite versions of itself from other timelines, including from timelines that don't even exist, and they all are omnipotent. Fans of the series tend to be relatively annoying and claim that their series is the best thing since sliced bread. No one in any other fictional universe can hope to defeat Demonbane, even if you say that you have a character that's omnipotent, Demonbane will still beat it because that's how it works.