[Matrixbeast]

Quote:

Originally Posted by Dr Kain

Gai is a selfish asshole. He didn't go to their wedding to show how he changed, he went to their wedding so he can die there, ruining the entire memory of what is supposed to be a happy moment. Every year when their anniversary comes up, they're going to think of the death of their comrade more than their wedding, and that is exactly what he wanted, to be the center of attention.

From the sound of that description, it seems like you watched the first 5 episodes then skipped the next 40.
The entire fucking point of Gai's character is that he begins as a dick but grows to become a decent person. Evolving from asshole to team player to nice guy. However, change is subtle. He kept his "Cool guy" exterior and loner tendencies because good character growth isn't about making a character take a complete 180 in personality.
He went to their wedding because he valued the team and didn't want to seem flippant by ditching it for the hospital (Stupid choice, but it was a kind gesture).

There have been moments in Sentai where things are left up to viewer interpretation, but Jetman's ending was so clear as day that in order to get your point of view, you basically had to ignore all the signs intentionally.