i-adjective
Describes a personality or attitude that is habitually inclined to see things in a negative, twisted, or envious light; often used for someone who feels slighted or resentful without good reason.
彼は僻みっぽいから、友達の成功を素直に喜べない。
He's so cynical that he can't honestly be happy for his friends' success.
僻みっぽい考え方をしていると、自分が損をするよ。
If you keep thinking in such a warped way, you'll be the one who loses out.