Hmm. Here's a list. I can't choose.
Lopunny Mega
Talonflame
Mega Alakazam (Modest)
Dragonite
Mega Manectric
I think Manectric is the most versatile, but it's hard to consider it a sweeper. Its better as a revenge killer. All of these have their flaws that make them weaker. I think Dragonite is the best if you build your team around it. I personally was never able to build a good team for it.