Plural of あいつ; derogatory or familiar, used for people the speaker looks down on or is close to. Often carries a rough, masculine tone.
Those guys are late again, huh?
When I left it to them, they made a mess of it.
こいつら and あいつら share the same rough, derogatory/familiar tone for a plural 'they', but こいつら points to people near the speaker while あいつら points to people farther away or not present.
あいつら points at people who feel distant or separate from the speaker, whereas 奴ら focuses more on looking down on or scorning them.
彼ら is the neutral, polite way to say 'they' for a group of males or mixed people, while あいつら carries a rough, derogatory or overly familiar tone.
Kanji spelling with 等 for plural; rarely used.
Rare kanji spelling using 彼奴.
Rare kanji spelling combining 彼奴 and 等.
あいつ developed from the older demonstrative pronoun あやつ under the influence of the parallel forms こいつ and そいつ. The plural or collective suffix ら produces あいつら.