This word is used to describe evil things, for example, crimes.

wicked?

回复 @圆环之理：Not exactly but this is the synonym of wicked.

vicious?

回复 @叶子保护伞：Nope, but some letters are right.

Is it an adjective or a noun?

回复 @于氏侦探：Adjective

回复 @啊啊是谁都对：villainous?

回复 @圆环之理：nope, this word is too long.

回复 @啊啊是谁都对：malicious?

回复 @圆环之理：nope, this word is also too long. But my word exactly ends with "-ous"

回复 @啊啊是谁都对：Uh, sorry, I cannot guess it

回复 @圆环之理：The last hint: this word consists of 7 letters and the last three letters are "ous"

heinous?

回复 @圆环之理：Yeah. You're right.