I'll start by saying that I celebrate most of his catalog as well, so this isn't an indictment of his career, just a commentary about this specific role.
Something I learned recently was that he was at least considered for the role of Tony Stark/Ironman, though I can't say how serious that consideration could have been. He had the martial arts/physical side of the role down, but he's just too much of a misanthrope to have been able to land the role that had so much external weight bearing down on it. I bring this up because there is a scene in the season finale that was similar to a scene from Iron Man 3.
The scene when Dr. Christie was being held by Wilson and co., was similar to when Tony Stark was being held by Mandarin's/Killian's men at the mansion in Florida. Both were vamping for time waiting for the cavalry to arrive, Stark's in the form of his suit, Christie's in the form of his army of twins. Because of the little nugget of information about him being considered for the role of Iron Man, I immediately drew this comparison. Maybe that was part of the original story before it was made into a TV series, and stalling for time is not a new concept, so I'm not trying to blame him per se'; it's just that I already feel like he's casting a long shadow over this series anyway and maybe this is some kind of nod to that story, like him subtly saying "if I had been cast as Tony Stark, this is how I would have played it. In fact, short of the suit and the violence, I see similarities between the two characters that I can't help but wonder are not coincidental.
So, it's not necessarily his acting that's the source of my irritation, more that I'm getting so sucked into the paranoia and conspiratorial nature of the show that I'm seeing things that probably really aren't there but in some ways make perfect sense, with Cusak's role being right at the center of it, and this isn't a traditional rant but I'm labeling it that because it's pretty out there like and not very rational, like most rants.
And that's how you start a fight by leading with your chin.