Why does Mister Sinister have such mixed reviews?

I've got a Mister Sinister that I plan on Awakening. I've also been reading up on him to see if he's worth it, but he's got very contrasting reviews, with some claiming that he's amazing and "hits hard after a few fights" and others saying that he's not good at all. Why is there such a disparity regarding him, and do you think he's worth Awakening?
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For me he's nothing but an AW defender simply because there's no fight I can use him for that I don't have someone else that can do the fight better. For others they may like playing him, his animations or not have alternatives/better options.
Simple.
its a very good ramp up ability that the awakened ability gives.
The most important ability of his in my opinion is his ability to pause debuffs.
parry, and if your quick enough you can make 2 heavies. The parry gives the stun, the heavy charging pauses it, meanwhile gaining a precision and a cruelty buff, guaranteeing a crit, which could be a decent number too.
However, I have him as a 6* - don't think he will ever go to rank 2 - he is alright, but for me there are so many better options than him when it comes to ranking a champ using a significant amount of t5 basic catalysts and t2 alpha's..
His awakened ability is actually quite good, once you defeat a certain class you will gain some extra fury, prowess, region, critical rating, power gain and precision for the next fight and you keep it with you the rest of the quest! (each class gives you a different 'buff').
So I think that the people who say that he hits hard after a few fights are correct!
Is it a mutant awakening gem? What other mutant champs do you have?
But then this is a game, go on with what you like!!
But, his problem is that he needs high sig and rampup for great damage, and he has kind of weird utility. I'd save the mutant gem for someone else.