That boss fight on hard was a pain in the arse. Have a full rage meter while going into the fight. Start the battle by whitling away his health by dodging and counter attacking where possible. Then about a quarter of the way through, rage the hell out of him. Also, try bringing in two pulse rifle powerups or the power ups of your choice (offensive preferably) from street fights to finish Leo off quicky when his health is below 50%. I hope this helps.