This is a very well made film showing an amazing visual imagination but it fails to integrate character and action and so is very disappointing.
The main conflict and the reasons for it are quite nice but the antagonist is too weak. He has an objective but isn’t nearly ruthless enough in getting it.
There is one point when the baddie could have got what he wanted by himself quite easily but instead he conjures up yet another fantastical creature for yet another big set-piece and stands back and watches. This particular creature was amazingly easy to kill but the sequence was dragged out, interminably, by Hellboy trying to hold on to a baby, inexplicably, instead of just giving it back to the mother - or some other person who isn't a target for the monster.
I nearly walked out despite the great mix of characters and often funny dialogue due to the pointlessness of much of the action. It's spectacular colourful imaginative action but lacking suspense, tension or any sense of real danger. OK, so that's like most big-budget Hollywood blockbusters but I expect more from del Toro.
While it's not particularly recommended, I can't really say don't bother seeing it either. CGI fans who don't care about logic - especially kids - will love it.