Quicksilver is a perfect example of why speedsters are so difficult to write properly. If he can move faster than bullets, why would he ever let an enemy finish an attack? He could disarm Ultron’s entire army before anyone even realized he had moved. Imagine giving Quicksilver a pair of Vibranium daggers and letting him fight Thanos. He could target the Infinity Gauntlet before Thanos even has the time to harness its power. The problem with speedsters isn’t that they’re too powerful. It’s that writers constantly have to find excuses for why they don’t use their powers to end fights in seconds.