My nemesis' power:
Power Via Blood
The blood of user may have mystical, cosmic or any type of special properties granting powers to the user. The abilities can come from the blood type, ex: flammable blood can give fire manipulation, acidic blood can gives acid manipulation or healing blood can gives healing skills.
Yup, that seems like a supervillain power.
My power:
Pessimism Inducement
The user can induce pessimism into anyone who is around them, and make them think more negatively about something. This can be used to make it so people may believe that something will never get better, about the world or about their live, and make it so they don't think positively.
Goddammit. Well, guess I have to make the most of it. I am Pessimism Man!
The fight:
Right off the bat my nemesis goes for his razor. As he reaches into his pocket I hit him with my super-pessimistic thoughts, causing him to become convinced that he'll never be able to actually break his skin because his mother never loved him. He drops the blade on the ground and sits down to have a nice cry. I grab the razor, but I can't stick him with it because that'll turn his power on, so instead I run away as fast as I can.
Eventually my nemesis gets over his sorrow and remembers that he needs to kill me. He grabs his backup knife, slits his wrists and takes to the skies like Alex Mercer from Prototype. Eventually he spots me in a boat, rowing furiously away from the shore, and flies towards me. As soon as he's over my head I hit him with my pessimism powers again, causing him to become convinced that he's terrible at flying and fails at everything he tries. The sadness overwhelms him and my nemesis plunges out of the sky and into the ocean, where his bleeding wrists attract Jaws. After his meal Jaws turns to me, but I use my powers to make him think he's fat and nobody likes a fat shark, so he swims away to go cry (or whatever it is sad sharks do).