If you actually had the powers and could prove you were the reincarnation of Jesus, you'd be crazy not to just prove it immediately. I don't even think you'd need to take over the world - you'd be the most powerful person the moment you made it clear that you were the messiah.
Even if you discount the population of Christians in the world, they would be a lot more unified and scary if they actually had a provable living messiah. I can also see a lot of conversions. Believing in one religion or a different one is pretty justifiable given that it's all faith for either of them, but it's a lot harder when you don't even need faith to believe in one.
And if you could actually fix everything, why wouldn't you? At least presuming that you're all-powerful such that you knew the outcome of fixes and didn't end up "accidentally" messing things up by trying to fix them.
Even if you discount the population of Christians in the world, they would be a lot more unified and scary if they actually had a provable living messiah. I can also see a lot of conversions. Believing in one religion or a different one is pretty justifiable given that it's all faith for either of them, but it's a lot harder when you don't even need faith to believe in one.
And if you could actually fix everything, why wouldn't you? At least presuming that you're all-powerful such that you knew the outcome of fixes and didn't end up "accidentally" messing things up by trying to fix them.