Can I avoid Rollback with drop table? I had a very long query running that was causing everything to get stuck. (was running for around 24 hours before being killed)
INSERT INTO tbl_new SELECT * FROM tbl_old

So I killed it. Now I don't really need tbl_new and it was empty before. The query is now stuck at query end stage which I assume means he's doing a rollback. Any way for me to avoid it? 

If I DROP TABLE tbl_new will that stop the rollback
Yes in InnoDB killing the session  is causing the rollback and the the rollback can take even more time than the actual insert command issued on the table.  

Refer the following:


  Beware of big rollbacks of mass inserts: InnoDB uses the insert buffer
  to save disk I/O in inserts, but no such mechanism is used in a
  corresponding rollback. A disk-bound rollback can take 30 times as
  long to perform as the corresponding insert. Killing the database
  process does not help because the rollback starts again on server
  startup.  


So you can use the InnoDb Recovery:  


  You can kill the mysqld process and set innodb_force_recovery to 3 to
  bring the database up without the rollback, then DROP the table that
  is causing the runaway rollback.


Hope this solves your problem.