Chen Changjie was a good player with a powerful smash. Liem Swie King had also a great smash - however in HK 1978 Invitational, Yu Yaodong beat him by 'out-smashing' Liem. Many singles players had great smashes, but for best, I would go for Harianto Arby. He could deliver a powerful smash from anywhere in the court. Still remember the way he beat Ardy in HK Open 94(?) with his smashes from the baseline, in the third set.