Talisman: Digital Edition

On the character select screen choose the Assassin as your own character then set your opponents as any character with strength of 3 or less, i.e Druid strength of 2. Start the game and keep playing until you roll a number that can land you on a square occupied by an opponent.

Choose the opponents square then select encounter character, choose to fight them then select assassinate. You will roll as normal but they wont so as long as they still have base strength of 2 or 3 you will win and unlock the achievement.