jump on it
(The hey is wrong with you?) No, you cannot kill Luigi in Super Mario galaxy. (He's too precious)
kill mario
No, she's good; she's on Mario's side. Mario can only kill bad guys.
Yes, but only with a star
You cannot really kill ghosts in Super Mario unless you have an invincibility star in use. However, you can stop them by looking at them, which makes them cover their faces.
You have to have (or be in) mini Mario form and kill the boss in world 5.
Jump on him. Jump on him.
kill the boss
Kill his ass
You run around it.
If you are referring to Super Smash Bros Brawl, then Sonic could KO Mario in a fight, sure.
Kill 800 enemy's