These achievement was actually the last one in the game I ever got. A normal game of Scrabble Flash goes until 1 of the 2 players reaches 25 points or higher. You are given 5 letters and you and your opponent take turns making words, once a word is made, it can't be remade. When making a word, you get points equivalent to the number of letters in the word. So if its a 3 letter word, you get 3 points with the maximum of 5 points for a word.
I suggest not going for this achievement by itself, but leaving it for last. As playing through the 50 episodes of Game Show mode, you will end up playing 50 games of Scrabble Flash. And if you were to win all 50 of the Scrabble Flash games with 25 points, that only gives you a total of 1,250.
In total you have to play a minimum of 60 games of Scrabble Flash winning every game with 25 points to reach 1,500 Lifetime points. Granted some games the CPU may win and you might have 20-24 points for that game and the if you play Scrabble Five-Letter Flash (which is the other game mode for Scrabble Flash) you only get 1 point per word. And those points do count toward the lifetime points.
And while racking up points over games, you should also get these achievements: