The ex-prez just filed a federal lawsuit against the network, claiming it's been pushing a lot of slanderous rhetoric about him these past couple years -- and he says it's all an effort to paint him in the worst possible light in anticipation of a 2024 run.

According to the docs, obtained by TMZ, Trump is pissed about certain labels he says CNN has used to describe him -- including "racist," "Russian lackey," "insurrectionist" and even comparisons to "Hitler." Those words simply go too far in Trump's mind, and he believes they constitute defamation.

We should note ... Trump's attorneys make a point about the alleged Hitler jabs, arguing CNN's repeated use of the phrase "The Big Lie" when referencing Trump contesting the 2020 election results is actually a direct reference to a term used by Hitler to incite hated of Jews and justify the genocide of the Holocaust.

So, in their minds, they see this as CNN associating Trump with Hitler by using the same term.

There's also this quote that spells out his beef ... "Beyond simply highlighting any negative information about the plaintiff and ignoring all positive information about him, CNN has sought to use its massive influence -- purportedly as a 'trusted' news source -- to defame the plaintiff in the minds of its viewers and readers for the purpose of defeating him politically."

Trump's team says CNN has blurred the line between opinion and news ... alleging it's now reporting these things about him as outright fact, which he says is a legal no-no. DT is seeking damages north of $475,000,000.