probably water main. You can build water main cancer teams which are rlly good obviously and the ninjas arent that hard to get. It will take some time tho. Also, water main has control (chaos) so you dont have to rely on other ninjas for one but the problem is you will have to use the critical chase and the chaos talent. Lightning main is also good since it has leech and would go well with gnw ninjas or sword ninjas and you can create immune teams with them; great for countering debuffs.