Forum superman.
-He has casually sped through timestop tech.
-Matched an out of control barry and wally.
-Casually matched professor zoom's speed with the latter admitting it.
-Made people like jay garrick and power girl look frozen.
-Matched barry and wally's speed by entering darkseid's dimension/singularity when both had to go 'faster than they've ever gone before' to get into it themselves. The same singularity that kept even high level green laterns out; no matter how fast they went, they were stuck in a timeloop. So superman is immensely faster than beings that regularly travel from the center of the universe (Oa) to the fringes. So much faster that he can power through timeloops that they can't.
-And just recently matched a new and improved wally.
The difference between max speed supes and max speed flash is a matter of percentages, not multiples.
I said before if barry and wally are cheetahs, supes is a lion.