This may not be scientific, and I could be wrong, but what I did is to just kill him as fast as you can. Take some potshots, get some risk in, get as little health taken as possible, and he should go down. Also try to hit him with the power punch combo whenever you're in range since it'll cut a chunk of his health. Still risky and close range so be careful.
Really, my guess is that the laser attack could be a design choice to let you know you took/stalled for too long, kinda like a timer of sorts. I don't like it either, but hey, it's beatable.
You're on a time limit (indicated by the boss bar's edge, it also causes the phases to change). Kill him before it runs out.