Polite ways of telling someone they suck?

I'm really sorry if this offends you, but did you know that when it was raining brains, you brought an umbrella?


Of course it doesn’t apply to you, you don’t suck

I need it to be not too direct, a bit subtle, and polite. Any ideas are appreciated.
Why are you worried about being polite? If it's something that needs to be said, then just say it. Someone has to.

I need it to be not too direct, a bit subtle, and polite. Any ideas are appreciated.
Why are you worried about being polite? If it's something that needs to be said, then just say it. Someone has to.
I’d rather not make this person angry, since they kind of have a short fuse. Why give myself something else to be annoyed about?
I need it to be not too direct, a bit subtle, and polite. Any ideas are appreciated.