This is just a man made opinion so i should not feel bad about liking heavy music if the intentions are not overt right?
It's not evil... It just sounds evil. :)
Any examples of tritone chord?
tritone is not a chord, it's an interval. Need three notes for a chord. I suppose any note on top of a tritone interval would be a "tritone chord". It's just dissonant. The idea that a musical interval could be "evil" is really rather funny.
The start of purple haze has it so does the song black sabbath by black sabbath.
It's also known as the diminish 5th, or augmented 4th.