That's what the site says:
'It should however be noted that sometimes having overall destructive capacity is not enough to defeat others that have "broken" or "hax" abilities.
Similarly, two characters in the same tier need not necessarily be equivalent in terms of power. The energy difference between them can range from negligible to absolutely massive, depending upon the tier.
It should also be noted that a character with higher tier cannot always beat a character of a lower tier, especially if their power levels are close to each other.'
So, Raphael being a 5-A doesn't mean that Veno can't beat him.