Easy "BOMBALICIOUS!" achievement
Complete the main storyline and have all shop equipment purchased. If desired you can also attempt this after obtaining the Golden Horn after the ninth princess in the main storyline. Then, play in Survival mode to easily continue after the Bosses. Get a bomb and the Golden Horn on screen simultaneously. Activate the Golden Horn, which summons three Tiny King enemies and a lot of other purple enemies. Wait for the screen to fill with purple monsters before exploding the bomb. Note: The bomb will not drop off the bottom no matter how long you wait. Simply kill the other monsters while ensuring that you do not accidentally trigger the bomb or any other ones that appear. Continue killing until the Golden Horn appears. If this does not happen, repeat the process until it does.