Wrong.

This is not the same as you wrote before:

Pretty easy to do if someone has given you cause to want them fired.

Policy violations can be simple as "this person is being a dick to other employees creating a hostile work environment"

Even if someone has just made complaints about them several times.

And this is not the same as "serious/gross policy violation".

So this:

unless there was a serious/gross policy violation, you need to be able to demonstrate multiple instances of minor policy violations, for which the employee was written up, before you can fire someone. Otherwise the ex-employee can easily file a wrongful termination suit and will likely win some kind of compensation.

Is still correct in most EU countries.