You will be fighting Matthew Patel in a small area with several plastic cups, glass bottles and chairs to pick up to use as weapons. Nevertheless, it is best to let those interactive objects stay where they are since they can ricochet around in the fight when Matthew Patel summons the four demon girls.
At first, Matthew Patel seems like a regular enemy with his punches. His basic attacks can be blocked. His fireball move, however, can’t be. Therefore, you should side-step when you see Matthew Patel with morphing a ball of energy with his hands. Dash attacks are really effective against the first boss in Scott Pilgrim vs. The World: The Game as long as he isn’t shooting fireballs at you.
Once you hurt him enough, he will summon four demon girls that will protect him with an invincibility shield. Carefully maneuver away from him and the four rotating helpers as touching them will harm you. Position yourself where you could attack the demon girls without getting in their path. Pick them off one by one to break Matthew Patel away from the invincibility shield. Afterwards, attack him the same way you did in the first part of the boss battle.
Once you damage him enough, Matthew Patel will summon two more demon girls. This time, these helpers can teleport and shoot fireballs at you. Fortunately, your main target won’t be invincible this time around. On the other hand, the demon girls are harder to defeat due to their teleportation technique.
Therefore, it is a good idea to focus your attacks on Matthew Patel instead and finish him off as soon as possible before you take too much damage. Keep in mind that your Special Attack makes you invincible for a few sections. So you may want to use that to your advantage in dealing with the last part of the fight. Once you defeat Matthew Patel, his demon girls (if they are still alive) will disappear along with him. Congratulations on beating the first boss of Scott Pilgrim vs. The World: The Game.