Sentinel with level 3 X-Factor demolishes everything. Without X-Factor, laser spit is faster than it was in MvC 2 (it was fast already), and now it does considerable chip. When X-Factor is activated, it gets even faster and can chip an entire team pretty much before X-Factor is over. Not impossible but it's sometimes demoralizing when one lone Sentinel can destroy a team pretty much as quick as an X-Factored Phoenix but has like three times as much health.