Somdev Devvarman was in three straight NCAA finals, winning the second and third. One of those years he beat Isner in the finals. (I realize, of course, that doesn't eliminate Isner from consideration.) He went 44-1 one year, too.
I'm not knowledgeable enough of college tennis to say those achievements are the bottom line, but they are the most impressive I know of.
There are two rules to success in life:
1. Never tell anyone everything you know.