There are 12 different characters and all have different special attacks. I managed this with my first character called 'Sea Mines' and their special is being able to deploy 3 mines that explode. Make it through the 10-12 stages and defeat the trio boss to complete the campaign.
Some levels I just kind of hung around the top of the map and they kind of killed themselves on some levels, including one of the mini bosses.
The final boss is a pain but from what I remember:
#1 stay far away and when he ground pounds jump over it and hit him once. Then try and run away or stay up high and when he stops land and let him do the ground pound again. After 3 hits you can set 3 mines off and hit them towards him.
#2 I couldn't find a strategy except for be aggressive. Hit him 3 times and set off your special. If you get hit make sure to pick up your body pieces.
#3 his most common attack is throw an electric arm forward so anytime he stops for a second he's probably gonna be doing this so jump and LT behind him and hit him. He also swings his sword around but I didn't see this on my winning run. Just try and be quick moving around.