Damian Lillard and Oscar Robertson are the only players in NBA playoff history to average 25 points, 6 assists, and 6 rebounds while playing in their first or second season. Both did it in their second season. Big O did in in 4 games in 1961-62, and Dame has done it so far in 6 games.
Here is a link:
Of course, Dame has at least 4 more games to go, thanks to his incredible buzzer beater!!!!!! And Big O's stats are much more impressive. But what's most impressive is that no one else is on the list.