Not sure if serious? I guess if Minato crept up on Flash while he was sleeping he might
be able to kill him, but even that isn't a given.
I'd suggest you read up a little on his abilities
. The phasing ability aside, the speed at which his five senses are able to perceive the world around him makes everything look like it's sitting still. At full speed, a drop of water dripping out of a faucet looks like it's taking hours to hit the ground.
Comparing Flash to anybody in this manga is just laughable. If minato were to even blink, then in the fraction of a second his eyelids were closed Flash would murder him 100 times over, and surprise butt rape the entire shinobi alliance.