Alliance vs iNfernity
During the 2013 "Summer of Alliance," the legendary Swedish team had the longest period of sustained dominance in the history of Dota 2. Between April and August of that year, Alliance entered over a dozen tournaments and failed to win only two of them, a feat unmatched before or since. So far ahead of their opponents was Alliance that casters and community took to the Dota 2 version of playing with one's food: giving Alliance "challenges" to add some variety to matchups in which victory was a forgone conclusion.
No challenge is more famous than caster Toby "TobiWan" Dawson's bet that Alliance couldn't take down a lane of barracks before the 10 minute mark (at the time, it was extremely rare for teams to break a base before 30 minutes). Alliance vs. iNfernity, a semi-professional Czech team that disbanded shortly after this match, isn't exactly a "great" game, and you can probably guess who wins already, but it does lay bare the earth-striding greatness of Alliance at the absolute zenith of its powers.