Liam did great....

...as did the rest of the cast. I've read a lot of posts saying how much they hated Liam Neeson's performance because he didn't smile as much as the original Hannibal did in the tv series.
Now, I've never seen an episode of the tv show (I didn't arrive in this world until 1988), but as far as the movie is concerned....
1.) Hannibal actually smiled quite a few times throughout the movie (after he gets rid of the attack dogs, after the gang takes out Tuco, when B.A. and Murdock argue about B.A. getting on another aircraft, when B.A. is yelling at the guys for locking him a cargo hold, while Face goes over his plan to nail Lynch, the end in the paddy wagon). I might've missed some more, that's plenty.
2.) Bottom line: if the idea was for you to play a character who'd been stripped of their rank (along with your best friends) because your friend/mentor (whom you believed had been murdered) helped in framing you and your comrades for a crime you didn't commit, then you wouldn't be smiling much either. Considering the plot of this movie, I saw nothing wrong with Hannibal/Liam's emotional expressions/acting.

"-Pain is inevitable. Misery is optional."