Wilhelm is Jack's enforcer. He is tough, powerful, can create and even lead units in battle. He is responsible for Hyperion's victory at the Battle of New Haven. He is feared by all of Pandora including the original four Vault Hunters and when he appears during "A Train to Catch", you are encouraged by your allies to run.
Wilhelm is a very powerful cross between a Loader and a person. He is rather similar in most functions to Warden. Use Corrosive weapons to get through his heavy armor and aim for his head to get critical hits. Use everything you've got and if you run out of ammo, check around the sides of this lake for ammo crates. When he starts getting low, make sure to really go after him because he'll start spawning Repair Surveyors which can repair him quickly.
He can also spawn various Loader minions including Badass Loaders. He can attack from a distance with various ranged attacks but he can also execute some devestating close range attacks including a spinning attack that hits anything within range.This isn't really a problem until you realize that he has jets on his feet which let him get around the area very quickly.
If you need cover, use the couple of trains scattered around the area. All there is to do is just keep pounding him.
