Yes, he's a badass. And yes, he's utterly ruthless with it. Make no bones about it, he crosses the line multiple times, clearly indicating a lack of basic decent morality... ... or at least, a lack of human morality. But are his actions justifiable in a Klingon context? Let's look at events from his point-of-view: he mentions unerringly throughout the movie that his motivation is to explore the possibilities of the Federation's new "weapon", this so-called 'Project Genesis'. He's blinded by this mission statement. He believes it completely, perhaps to the point of being unable to see/accept any possibility that it was designed with a more benign purpose. He is clear within his own mind that Starfleet is developing biological weapons of mass destruction for use against the Klingon Empire, and having convinced himself of this 'fact', he feels no shame is taking pre-emptive action to try and uncover the 'secret'. Up to and including many dishonorable things, like taking hostages and murdering them. Undoubtedly he is also blinded by the power that Genesis could bring him. If not as a physical weapon for his own personal use, then (surely) in terms of the noteriety it would give him back on the homeworld. Having uncovered and single-handedly stopped the Federations "secret" plans to apparently annihilate the Klingon Empire with this Genesis weapon. I can see him spinning this, to the point where honor is granted to him, the High Council makes him the Chancellor, he's inducted into the Great Hall Of Warriors, etc etc etc. So. Kruge is the baddie. He's a bad guy. But... in his own mind... was he doing the right thing all along?