The best I’ve done with Tusk (in training mode) is 95% without counter breaker, but a counter-breaker on that last skewer should easily do the trick past 100% damage ^^
The thing is, during that combo, there are plenty of breakable opportunity.
Backstab > s.HP > cr.MP > s.HK > shadow Skul Splitter > HK (manual) > shadow Skull Splitter > auto HK > light shoulder > auto HK > Conqueror Ender > Skewer
And you’re at 95% damage combo. But like I said, it’s easily breakable, espacialy on those auto HK, so you can mix them with manuals (HK or MK). Also if your opponent have the right timing to break those shadow Skull splitter, you also can counter-break them…
I’ve never done it in a real fight, but it’s more because of that first Backstab.