YOU SAID:

Its personality is fairly malicious.

INTO JAPANESE

性格はかなり悪質。

BACK INTO ENGLISH

Character is pretty bad.

INTO JAPANESE

性格はかなり悪いです。

BACK INTO ENGLISH

I have a pretty bad personality.

INTO JAPANESE

私は性格がかなり悪いです。

BACK INTO ENGLISH

I have a very bad personality.

INTO JAPANESE

私は性格がとても悪いです。

BACK INTO ENGLISH

I have a very bad personality.