多少、あいつおかしいぜ。
More or less, he is crazy.

厚顔無恥とはまさにあいつのことだ。
He's such a shameless jerk.

あいつは善悪の区別がない。
That fellow can't tell right from wrong.

あいつは小山の大将だった。
He was the cock of the walk.

あいつは執念深いから気をつけた方がいいよ。
Watch out for him. That guy can really hold a grudge.

あいつは簡単にはくたばらない。
He has more lives than a cat.

あいつは一家のつらよごし。
He is the black sheep of the family.

あいつは図々しい奴だ。
That fellow is a cool hand.

あいつはいつも親に金を無心している。
That guy is always asking his parents for money.

あいつはいったい何者だ？
Who the devil was that?

あいつは、お仕舞いだ。
He's a goner.

あいつの多芸は無芸のたぐいだ。
He is a jack-of-all-trades.

あいつとは断固２度と口をきかんぞ。
I absolutely will not speak to that fellow again!

あいつとは今後関わらない。
I've done with him for the future.

あいつでかいことばかり言ってるけど、そのうちぼろを出すよ。
He's always talking like a big shot, but it won't be long before all his faults are exposed.

あいつが臭い。
He looks suspicious.

あいつがガッツポーズするなんて、よっぽど嬉しかったんだろうな。
It must have been something really big for him to strike a triumphant pose like that.

あいつ、上司に胡麻を擂ってやがる。
He is buttering up to his boss.

「あいつはいい奴だ」と皆が異口同音に言う。
He's a nice guy - that's unanimous.

あいつを撃つ。
I'm gonna shoot him.

いや、あいつは「純」というより「鈍」って感じだな。
No, I feel like he's not "pure", but rather "dull".

誰だ？あいつ。
Who's that guy?

あいつがトム？
Is that guy Tom?

あいつらはよそから来たんだ。
They came from somewhere else.

あいつケチなんだ。
He is a miser.

あいつなら昼飯食ってるよ。
He is having lunch.

あいつ、高給取りだよな。
He is a highly paid man.

トムの考えは賛同できないところも多いけど、あいつの文章の読みやすさは見習いたい。
I don't agree with most of Tom's thoughts, but I aspire to be able to write something that reads as fluently as his compositions.

あいつは絶望的だよ。
He's a goner.

あいつは気狂いだ。
He's crazy.

あいつ、やる気満々だね？
He's very motivated, isn't he?

俺らの問題なんて、あいつのと比べたら屁でもないんだよ。
Our problems are nothing compared to his.

あいつ誰？
Who's that guy?

遠くからでも体型と服だけであいつだとわかる。
Even from afar, you can tell it's him just by the shape of his body and his clothes.

僕のカメラの方があいつのより格段にいい。
My camera is much better than his.

あいつの卑劣なたくらみをみんな見透かしていた。
Everyone saw through his despicable schemes.

あいつの話は胡散臭い。
His story sounds strange.

あいつ癇癪持ちだから。
He has a quick temper.

あいつ、異性の友達多いよな。
He has a lot female friends.

あいつ、高校を中退したんだ。
He dropped out of high school.