"To chew out" is a good one, it's not really informal but you wouldn't usually talk to your boss about how your wife chewed you out. To berate is a more formal way of saying someone criticized your badly. To scold can be used as well, although it's most often associated with children.

If you want something slightly crass, then "tear someone a new one" is possible. If you, as a boss, criticise an employee for doing a poor job, then you "give him/her a dressing-down".

Yes, 'slag off' is a good one, if you want a colloquial British phrase.

In British English, we might say 'to slag off'. This is very colloquial. 'Stop slagging me off' would mean 'Stop saying bad things about me.' Another option might 'to hammer' someone. 'My boss really hammered me today', you might say. However, 'I got hammered' can also mean 'I drank a lot of alcohol.' Ah! The wonders of language.

Insult, would be a more formal one.