[quote=Dynamics]
But something has to be more effective on him than others, right?
[/quote]

Vex: Get his suit off him, then yeah. Energy attacks. What physical attacks there are can hurt him, he can overcome with his fighting skill. His suit is extremely effective against energy attacks and physical attacks alike, and has a unique self-repair function. It's incredibly hard. Not to mention it increases his reaction time and other physical attributes.