Yes, Wittmann (138 kills) was one of the greatest definitely. Having looked into the German tank aces, the greatest of all was Kurt Knispel, who is my current profile picture. He destroyed a confirmed 168 tanks, and possibly as many as a total of 195. Other great tank aces includes Otto Carius (100-110 kills), Ernst Barkmann (82+ tank kills with 136 miscellaneous AFV's, and 43 anti-tank guns ; [from Flames of War]); Johannes Boetler (139 up to 144 kills); Balthasar "Bobby" Woll, Wittmann old gunner (82 kills); Paul Egger (113 kills), who started off as a Luftwaffe pilot, fought in the Battle of Britain flew 112 combat missions and was shot down 3 time, and then went to the Waffen SS; as well as others. Fascinating history!