完蛋了 means: Done for; ruined; finished; goose is cooked. It is the Mandarin counterpart of a Cantonese term "玩完" (game over)
I am curious about what 蛋 is referring to. Without any reference, I can only speculate
蛋 is a nickname for 'testicle'; 完蛋 simply means "f~king finished"
When a chicken stop laying egg, it is doomed and will be slaughtered soon
When an egg (蛋) is finished (完), meaning an egg is broken, it is ruined beyond repair
Which is the correct answer? If none of the above is correct, what is the correct explanation of 蛋 in 完蛋了
I think #3 makes more sense (finish like an egg is broken)