If I remember correctly, you have to keep mashing the buttons to keep all the bars full until the timer runs out.

You think that one is hard wait until you get to 220 with Black Adam 3 Stars is impossible

Left thumb on Button 1, right thumb on button two and just tap them up to full bar and maintain for 20seconds.

I haven't finished all Star labs but I can assure there are worse missions

I remember Harley Quinn's with Two-Face in the background. Whoever put the hint "Jumping can evade Two-Face's gunshot's." is a dumbass. It doesn't work to jump.
Two-Face will randomly choose between Heads (You), and Tails (Catwoman) every 4 seconds. One of the stars was don't get hit for 15 seconds. It's nearly impossible because Two-Face will just shoot you eventually before 15 seconds elapses.

I ONLY beat it with three stars because Two-Face randomly said Tails 7 times in a row.

it was hard but far from impossible, I just 3-starred all star labs missions yesterday, I had to beat 220 three times to get all three stars, but it forced me to learn mean combos with black adam. After I got the first star, I had no problem beating the mission 2 other times, just gotta be supper aggressive and dish out 35-45% combos with black adam