Marvel's Avengers only have a few boss fights in the 12-hour campaign, however, they're pretty well scripted and provide a pretty thrilling experience. Abomination's boss fight, for example, which takes place in the game's opening sequences, is one of the most memorable boss fights in the game.
Monica Rappaccini is one of the two main boss fights in the game, and it can get pretty overwhelming for some players as it has multiple phases that can get quite difficult. The fight against Monica takes place in the mission "To Stand Alone". The boss fight takes place in three phases, and you have to focus on staying on the platform in all three phases. Falling will expose the character to poison gas which can quickly deplete their health.
During the first phase, Monica uses basic attacks that can easily be evaded. Keeping a safe distance with her and using Black Widow's pistol should quickly deplete her health, however, getting too close will cause her to use melee attack, which can prove to be a bit of a problem. Around the second half of the first phase, it will disappear and a few drones will appear instead. Take out the drones with your pistol to make her reappear on the battlefield.
From the second phase, it becomes a bit tricky. Monica starts running towards you if you try to maintain distance, so you need to time your dodges well enough to avoid attacks. The rest are pretty much the same, with ranged attacks doing most of the stuff. Unlike the first phase, Monica summons proto-synthoids this time around, which can be quite difficult to deal with. Make sure you use your abilities properly to avoid being overwhelmed. Knocking down the Synthoids will cause it to reappear.
The final phase is pretty straightforward. She dives into the air and slams to the ground during this phase, however, it's fairly easy to dodge this attack as long as you pay attention to the ground impact indicators. Patience is the key to the endgame, as the slam attack can prove to be problematic if you get too ambitious.
