Depends on your definition of strongest honestly. Each has something they are stronger at then the other two.
Lance is the strongest physically and emotionally. He grew up in Ishgard and serves in Coerthas after the fall of the Steel Vigil. The men in his family expect strength an steel from the boys.
Dest is the strongest magically. The other two have very little to no skill in magic or manipulating aether. Yet Dest has the strongest heart when it comes to caring about others.
Karigan is the strongest when it comes to speed an cunning. She is extremely light on her feet an quick to look for openings in a fight. Though that does sometimes backfire on her for sheer bad luck.
So each has something they are strongest at. It’s not something I can easily pick between.
@neoma-eltanin thanks for asking!
Spirit of the Warlock 