Darth...this is assuming that he has The Force...
If we are going by actors...well...James Earl Jones would get owned...Sabastian Shaw would blow ass...Jake Loyd would die of fright...Hyden is too much of a little pretty boy...C. Andrew Nelson might be able to hold his own against Leon...but out of everyone who has played Vader I give David Prowse the best chance of taking down Big Van.