Not a movie, but Naruto applies here.
Yeah, Naruto fell off DRASTICALLY after the timeskip. Lee versus Gaara >>>>>>>> anything from Shippuden.
I nominate the Breakfast Club. That movie was the TRUTH (
) until Allison got her makeover. After that...
...and
at Brian getting stuck as the fifth wheel doing everyone's homework at the end
"Don't You Forget About Me" is still a great tune though
...
Another nomination (Unpopular opinion warning)... I'm gonna say X2. The opening scene with Nightcrawler was TURNT, and the mansion attack was also flames
When Colossus came out
The 3rd act, however, was kind of weak though in comparison. Wolverine was the only X-man we got to see doing any real fighting in the climax when that should have been the whole team shining against all of the bad guys in an all-out battle royale. (Especially Cyclops, who desperately needed some shine after getting captured early and missing a whole hour of the movie.)
When you peep the best stuff in the comics and the 90's cartoon, you'll see ALL of the characters fighting as a unit, and that was sorely lacking in X2, even though it's a well-done movie on a technical level.
^^^We should have seen more of that.