Tifa can beat a godlike being to death, the two just aren't comparable.
Watching the movie Advent Children when they are fighting, they seem pretty similar. Tifa may be able to kill final fantasy gods but she doesn't seem unusually powerful. For example, they need bombs to take down reactors rather than her destroying the entire building herself. On this forum if you were god tier you could easily obliterate the entire city yourself and then some. She needs help against shinra gaurds in game as well, who are random people, but of course at max level she could likely obliterate a large number of them. In story, however, in another ff7 game, someone of Cloud's level was able to be killed by a group of them. They were a decently sized group to be sure, but not too insane. I guess they could also be superhuman powered despite seeming like random people to explain this, but they don't really go into their characteristics too much. If they are superpowered than everyone is likely better than humans of our world.
While I thought a rematch of a Death Battle for revenge purposes could be interesting, I would be willing to make a character of possibly similar style that's a higher level if you guys are not convinced. Don't mistake me for thinking Tifa is low tier or anything, but she's not a super high tier either.