Run was the movie that allowed Madhavan to break away from his romantic hero image and play an action hero. For the first half hour or so, you don't even realize it: all you see is him chasing Meera Jasmine around, singing songs and doing his usual shtick.
Then comes the scene in the subway, where he is cornered by some of her brother's men. He starts running and goes right up to the exit only to pull down the shutters. Turns, looks at his pursuers, waits for the first one to come at him and lays him out with a single savage blow. Crocks his head, gets a wild look in his eye and walks towards the rest.
Honestly, I didn't think Madhavan had it in him to do that. He is so effective in that moment that it makes the rest of the movie work wonderfully.