This indeed did the trick. Didn't think a pipe wrench would have that much grip. Thanks for the tips peeps

 

What I do is to take a C-clamp and clamp the belt together (across the tensioner) thereby making it as tight as possible (I keep tightening till the belts touch each other). That holds the water pump from spinning and allows me to use a pipe wrench on the nut. Hit the handle of the pipe wrench with a hammer and it will eventually shock loose.

 

good deal, glad you got it off

 

To be more precise I used a size 18 pipe wrench and locked it on the dead pump pulley's lip (which is completely destroyed now, so NOT a good idea to try this method if you're planning to keep the pump.) And then I used a Massive adjustable wrench on the bolt.

Big pipe wrench and massive adjustable wrench is a killer combo