Bloons TD 6

You can get this achievement a lot faster by allowing your games to move into Free Play mode, where more BADs spawn than you will typically see in your medal games. Additionally, utilizing towers that are strong against MOABs (Super Brittle, MOAB Mauler, Beast Master Megalodon, MOAB specialized cannons, etc.) will help you go a lot further. This, in turn, helps you encounter more BADs.