Sonic's running speed in the comics is often portrayed as superhuman and hard to measure precisely. It's one of his defining traits and can change based on the plot and the author's imagination.
In the comics, Quicksilver's speed is off the charts. He can move so fast that it seems like time slows down for him. Different storylines might give slightly different estimates of his top speed, but it's always insanely fast.
In comics, the speed of the Flash varies depending on the storyline and the power levels given to him. Sometimes he's shown moving so fast that time seems to stand still for him.
To start writing space marine fanfiction, begin by choosing a particular aspect of space marines that interests you. Maybe it's their weapons or their training. Then, think about the setting. Will it be on a war - torn planet or in the depths of space? After that, develop your characters. Give them distinct personalities and backstories. Don't forget to add some conflict, like a powerful enemy or a difficult moral choice.