To be fair, that didn't really happen in MSG. In fact, 0079 is really unusual because the final battle is actually a grudge match. Char and Amuro are basically two rival aces, but they're small points in the massive battle.
Like, Amuro never meets Gihren, even though Amuro seems to be able to sense that Gihren is responsible for all this. (He can even pinpoint where he is.) It's Kycilla who shoots Gihren, and it's Char who murders Kycilla immediately afterward.
In a modern Gundam series, Gihren would show up in the Gihren Gundam, and Char / Amuro would team up to fight him. Then he'd give a speech about how he's actually doing all of this because of a power-trip, and waves of Newtype energy would make everyone stop fighting.
I'm pretty sure 00 ended that way.