There are so many villains that batman has faced, let alone the DC universe, but here are the top 4.
1. The Joker
The last time we saw the joker on the "big screen" he was portrayed by Heath Ledger, and he did a fantastic job. Jared Leto, the new joker, says his Joker will be the best one yet, high hopes Jared.
We haven't seen deathstroke in a movie as far as I know, only on the TV show Arrow, and it was awesome.
3. Red Hood
I would personally love to see redhood (Jason Todd) be the bad guy in the reboot, it would be highly unlikely to happen but it would be cool.
4. Mr freeze
The last time we saw Mr freeze in a movie he was in that god awful batman & robin. It would be good to see a grittier version of the character.