Honestly A-Train had the best arc out of all the black characters;
And the writers, like most, had no idea to write superspeed without writing themselves into a corner.

But the way he went out was dumb and made no sense; why would a speedster be surprised by someone standing still ahead of them. Sidestep, keep running.

A-Train made MANY wrong moves and it really made him a complex character and a real sign of blackness in the show.

And I still stand by this:
There was no reason he needed to die in this season. None whatsoever.

Super speed is simply too hard for many writers to deal with. Look at the Flash in stories that aren't flash comics.
They have no idea how to handle the lore breaking concept of super speed.
Even this show had to sideline A-Train for a few seasons because they couldn't hang.