no
If he wants to.
Yes because joker killed Jason Todd the second robin
Yes, the joker did kill people in the movie Dark Knight.
A joker is either someone who enjoys making people laugh, someone who makes people laugh as a job, or someone out of batman.
The Joker could beat him up. The Joker would try to kill Luthor with his gun. It'll just stun him so Joker could knock him out. Joker knocked him out with one punch in the face. Joker wins.
a joker
Many times (In the movies and TV shows) Batman has threatened to kill The Joker. He has never carried out his threats because it would violate his conscience. There are many comics where Joker does die and I believe there is an alternative comic called 'The nail' where Batman kills The Joker.
The Joker.
The joker
Yes, and some of them were his henchmen.
Joker