Dungeon Siege III

Have 1 Game Save set as a High 19th Level Character. Load That Game & have Another Player Join (On-Line & Local Work). Have them pick a character. Go out & gain the level. Once acquired, Return to main menu, then load that Game Save again. NOTE: Must return to the menu cause if you reload that save from the in game menu, the secondary character stays the same as previously selected. Have Other Player choose a Different Character, rinse & repeat. Then just return the favor to the other player. Easy 60 Points!

You can get this achievement by playing normally or by joining another player's game session just before his characters earn the level 20 and choosing Katarina. This is available for other characters.

You can boost a friend and offer him this achievement by creating a save just before passing level 20 and inviting him in your game for the level gain.