"The best over ever" would mean the best over that any bowler has ever bowled.
However, "Andrew Flintoff the best over ever!" isn't a proper sentence, nor does it make sense as a title or headlinese. So really all we can do is guess at what whoever titled the video probably meant.
I imagine that they intended to say that it was the best over ever by any bowler, but that Andrew Flintoff was the one who bowled it, in which case they should've said:
Andrew Flintoff bowls the best over ever!
If they intended to say that it was his personal best, but not the best from any bowler then they should've said:
Andrew Flintoff's best over ever!
Andrew Flintoff bowls his best over ever!
Note that sometimes when someone says that something is "the best ever" they are deliberately exaggerating and don't mean it literally. Or they are being ironic or sarcastic and mean that the thing was quite bad. Or sometimes they mean that the thing in question was subjectively very entertaining for some reason, but not objectively the best - so an example of that might be a particular over bowled by Andrew Flintoff during which a number of unusual things occurred such as a bird attacking him, a streaker on the pitch, a batsman who tripped over, etc.
Note: for those who don't know, "over" is a term used in the sport of Cricket.