Fastest way to beat Fontaine ON HARD! 1:17 - Bioshock
I beat Fontaine in little over a minute. I beat him using just the Target Dummy plasmid and my wrench. I use these tonics: (as well as others, but they aren't worth mentioning)
Wrench Jockey 1+2, powers up my wrench
Wrench Lurker 1+2 critical damage with wrench when enemy isn't aware of me (when his attention is to the target dummy)
Sportboost 1+2, speeds up my movement and whacking speed
Bloodlust, it restores any lost health and eve by whacking my enemy will the wrench
I use the Target Dummy plasmid to direct all of his attention away from me while I whack away at him with my wrench.