凄艶 （セイエン） weirdly beautiful

凄惨 （セイサン） ghastly, gruesome, appalling, lurid

凄い （すごい） terrible, dreadful, amazing (e.g. of strength), great (e.g. of skills), wonderful, terrific, to a great extent, vast (in numbers), awfully, very, immensely

凄い事になる （すごいことになる） to go crazy (esp. of a situation or thing), to get out of hand, to end up in an extreme state

凄まじい （すさまじい） terrific, fierce, terrible, tremendous, dreadful, awful, amazing, absurd, cutthroat, intense