Timecop
(1994)

Max Walker (Jean-Claude Van Damme) tricks the old Senator McComb (Ron Silver) into meeting his old self back in 1994, then pushes the two incarnations of Senator McCombs into each other. Since, we've been told, two versions of the same matter cannot exist in the same space at the same time, both Senators melt away and die painfully.

When Max leaves 1994, and returns to the present, he finds that everything has changed for the better! As far as the world knows, the evil Senator McComb disappeared without a trace in 1994, so none of his crimes ever happened. Max's deceased partner Sarah (Gloria Reuben) is alive again, though she doesn't know or recognize Max. And best of all, Max's wife Melissa (Mia Sara) was never killed by McComb's henchman. When Max returns home, he's reunited with both his wife and the child (now 9 years old or so) she was expecting at the time of her "death."

Thanks John L!