This page of Marvel's Avengers guid has a description of the fight with Taskmaster, one of the bosses. You will learn when you confront Taskmaster, what attacks the boss has and how to avoid them, and how to defeat him effectively and quickly.
The final stage of The light that failed mission makes you play as Black Widow. You must confront the first boss named Taskmaster and stop him from detonating a sonic bomb on the Golden Gate Bridge. During this duel, you will have to use several essential mechanics, like dodges and counters, to deal with this supervillain.
First phase of the fight
When the fight starts, run forward, jump off the bridge, catch the Taskmaster in the air and focus on performing the quick time event - press the right buttons at the right time.
Second phase of the fight
After a short flight, the battle moves to one of the narrow platforms of the bridge. You have to dodge sideways when the Taskmaster charges at you. After that, you have to immediately shoot your opponent to inflict some damage. You don't have much time to dodge - when the opponent is close to the Black Widow, time will slow down a bit.
When dodging, hold the button responsible for aiming and immediately shoot Taskmaster in the back. Shots from the front will be blocked by a shield.
Third phase of the fight
After several accurate shots, Taskmaster's jet pack will get destroyed. The fight moves to the roads. During this phase, focus primarily on dodging (just before you get hit) to perform a counter. Combine light and heavy attacks to make combinations that are difficult to block. Don't attack the boss for too long, he will eventually counter your attack.
Fourth phase of the fight
In this phase, you have to use grapple hook to counter the opponent's ability and avoid receiving damage from bombs. Wait until your opponent starts the skill animation (he spins around) and press the counter button (R2 on PS4). Keep doing this until you reach the final phase of the fight.
Try to use the grapple when the opponent is near the red circles. It is possible that after a successful counterattack, Taskmaster will get in the range of his bombs and receive additional damage.
In the final stage of the duel, you will have to use the Veil Of Shadows Heroic Ability to disappear from your opponent's field of view. Perform several attacks and use a finisher on Taskmaster when the information appears on the screen.