sullivan

when u fight him try use hand to hand until he is on his knees then hit him with a strong fast melee weapon and then repeat this also when u fight him bring some pain killers its not needed but it helps

Use the knife gloves! bowie knife boxing gloves. He cant disarm them and they are pretty effective. and make sure you have some good healing items

throw things like the ax hammer thing it takes a chunk of health and before you fight him i would recommend you to kill all zombies in the downstairs room they get to be annoying and heres a hint the flairs he throws at you throw them back at him get about two of those up their and boom hes finished but if to hard cout his rounds while hidding then when hes reloading throw ur weapons at him not as affective but still okay

When I beat Sullivan all I did was grab a couple of sledgehammers and get at least one quickstep and have untouchable, painkiller, and repulse. But when he throws the flares do NOT try to throw them back because if you don't throw it in time you will be a gonner and then you will have to start from the elevator again. Just to be on the safe side you might want to bring a nector or two just to throw down into one of the holes