Darth Scion vs Lucien Draay

Random fight; no prep; 20 m start; neutral ground; all-out fight

Sion killed better.

Darth Sion has better feats from what I've seen: beating early-mid game Exile and killing one of the jedi masters (it should be noted that while Lucien did beat all of his fellow convenant leaders, they were all far less trained for combat and were seers primarily). 

Further while its often viewed as unimpressive, Sion was ultimatively near-immortal, and has a bigger variety of useful force-abilities

Lord of pain wins