How to say “Badass” or “Cool”

かっこいい or かっこいい  badass or good looking/cool looking

日本の足袋は かっこいいです。
Tabi (traditional workman socks) that of Japan, is really cool looking (badass!)

You can also use カッチョいいー! or カッケ―! for extra slangish conversation.

この 音楽 めちゃ かっちょいい! 
This music is so badass! ( This music is such a blast!)

スゲエ かっけー!
Wow definitely badass! (or This is definitely a blast! )