悪 bad

You can remember the Onyomi because the Japanese word for "demon" is AKUma!

A heart that is sub-normal is bad.

pathetic / gross ★★★★☆
気 (mood) + 持 (hold) + 悪 (bad) = 気持ち悪い (pathetic / gross)

has two meanings: If you say it about yourself, it means you feel terrible. If you say it about someone/thing else, it means,"That's gross and pathetic."

the worst XXX EVAR. ★★★☆☆
最 (most) + 悪 (bad) = 最悪 (the worst XXX EVAR.)

(say hi to) the Bad Guy

★★★☆☆
悪 (bad) + 人 (person) = 悪人 ((say hi to) the Bad Guy

)

talking shit about someone. ★★★☆☆ KUNKUN
悪 (bad) + 口 (mouth) = 悪口 (talking shit about someone.)