Well yeah! There's loads of reasons why villains can get worse and more evil. Some might be through circumstance, others can simply be depraved. It depends on the heinous criteria as well...
A villain who crosses the MEH (Moral Event Horizon) multiple times through horrendous acts (i.e: unjustified/unnecessary murder or rape, the latter is always an instant cross in the meh). As well as shedding any redeeming qualities are almost certain to become Pure Evil...
There are many types of Pure Evil, some born bad, others became that way through twisted events.
