"Meaner"は昔から使われている比較形容詞の正しい形です。"more mean" も英語圏でよく使われる表現です。
He's meaner than he looks.
I just want Carl to be a little meaner.
You know, you're meaner now that we live together.
If I don't eat I become dumber, meaner.
Dads are meaner, tougher, hairier.
Bigger, uglier, meaner than before.
Our Professor X was way meaner than this guy.
Maybe stuff like that just makes him meaner.
Bad Chuck Wilson and meaner Bobby Lowe, and three of their acolytes.
He's meaner than a shifty salesman.
And like a starved dog, it's meaner than ever.
There's nothing meaner or stronger than a vampire.
He was one of the meanest rulers the country ever saw. Even meaner than his predecessor, who was mean enough.
You are more mean than you used to be it seems.
Who is more mean to you--your sister or your brother?
Nothing is more mean to the earth than to treat it with ignorance and disrespect.
He is more than a little mean. At least that's what many people have told me.
Is he more mean than a junkyard dog? Or meaner than an angry wolverine?
More mean or meaner--which is correct?
You are more mean than you used to be about these topics.
She couldn't be more mean about her wealth and social status to those who are pooer than her.