I'll Take care of it - Acting like you're the hero who's going to save the day, but

Acting like you're the hero who's going to save the day, but you're really the villain who lets everything go to hell.

'I'll take care of the homework', then he forgot and got a zero.

'I'll take care of the dinner', burned the food and yelled at the cook.

'I'll take care of the project', left it for the last minute and it was garbage.