Is it OK to say, humorously or in a threatning way: I'll send you to retirement!

No, it doesn't really sound meaningful. Please supply some specifics of the situation.

Let's say I think you're old and you shouldn't be doing what you're doing, I think you should quit, it's high time, so, just for fun or in a bit threatening way I say something like: I'll send you to retirement.

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A little rude, I think. This is more current humour: 'Have you thought about taking early retirement?'
Mister MicawberA little rude, I think.

This is supposed to be a little rude. So, I understand that as far as grammar and meaning are concerned, everything's fine with my phrase?
No, it is not natural. And certainly a learner-- or anyone-- should try to be a little rude. What is the matter with you, anyway?
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Well, maybe there's no such an equivalent in English.

Let's say there are two boxers. Before the fight one of them says to another: I'll send you to retirement!!! (meaning I'll kick your ass and you will finally quit) and the other one, much older, says: Will see, dude!

Maybe: Have you thought about taking early retirement?" fits here, but I think it should be something coarser.