Kogami is the good kind of bad ass.
Spoiler for Kogami moment of bad ass from latest episode:
He's the sort of bad ass that strolls through an all-girls school like he owns the place, and then walks in on the female criminal, gets her identity, and without flinching prepares to blow her away with a Dominator.
It doesn't matter how hot or moe you are. Mr. Bad Ass doesn't care.
On the other hand, he shows warmth (to Akane, and even a bit to Gino) and just the right amount of professionalism. He's a bad ass with a heart and style.
And yeah, like Kaioshin said, it helps that he has great detective skills.