Which do you think is the most despicable?

A crooked cop - reason;

The cop has some power to prevent most if not all of the other scenarios.

A crooked terrorist, married, with a law degree and children who cheats with someone on the wrong side of the border.

Terrorists get the vote from your list.

Crooked cops get a close second if they engage in police brutality. Otherwise I don't really care what they're doing. There's worst stuff people do.

Gangsters are just dumb and join gangs for a lack of independent thinking skills.

Immigrants just want to get out of crappy situations.

Lawyers are just doing their job.

Cheaters are none of my business.

As for people I hate, child abusers which failed to make your list.
I don't really care for religious extremists who force their beliefs or drugs cooks either because both those groups are fucking up the society I'm living in.

An arrogant hipster.

Terrorists win for the worst.

A crooked cop is a despicable thing, a cheater probably worse, but a terrorist actually hurting or killing people (or planning to do so)? That's a completely different league.

They're all bad, except lawyers, some lawyers actually do have integrity and values. Defense attorneys are usually pretty bad.

The killers are the worst for sure. Terrorist followed by Gangster.

OP is most despicable of all

me?

What is despicable?!

I would pick all of them.