The most common and most likely answer to this crossword clue is the 8 letter word EVILDOER
I've seen this crossword clue in The Sunday Telegraph
E
V
I
L
D
O
E
R
More clues leading to the result EVILDOER
- Reviled old rogue?
- Be upstanding to execute Queen’s offender
- He should be in Nick‘s wild revel, one engaging cook
- Villain or devil incarnate, ultimately infernal
- Baddy, at any point in time, receiving unopened sex aid
- Deliver criminal, arresting old villain
- Stay up with Her Majesty after party for criminal
- Bad person devil corrupted, poet’s concluded
- Villain will make lover die
- He is no good, always carrying broken idol
Buddy explains!

The straight part
We know that "Bad person" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bad person = evildoer.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EVILDOER mean?
EVILDOER noun- A person who performs evil acts.