Stubborn Strategy

"Just because a thing can be done, does not mean that it should be done."

- Achievement description

Stubborn Strategy is a hidden achievement added in Bloons TD 6 in version 22.0. It requires the player to beat 100 games on maps with removable obstacles without removing the obstacles. The map or mode for the game doesn't matter. It awards 500 and 3 Cash Drops.

Strategy
This achievement is more grindy than skill-based, since most maps which can satisfy the achievement are not necessarily difficult. For most maps, removing obstacles is not necessary nor particularly helpful.

But if really desperate, try grinding on Skates on Deflation Mode with Gwendolin + 3-2-0 Destroyers + 4-0-2 Bloontonium Reactor. Using The Cabin will also work.

Some maps with removable obstacles that can be beaten without removing them are the beginner map Skates and the intermediate maps Encrypted, Bazaar, KartsNDarts, Haunted, Downstream, Firing Range, Cracked, Streambed, Rake, and Spice Islands. The intermediate map Chutes is not recommended for this due to it being difficult to beat without removing obstacles. Advanced maps and Expert maps that have obstacles are not recommended either (with exceptions such as Spillway, Cargo, Another Brick and Dark Castle), as they are also hard to beat without removing any obstacles. Beginner maps other than Skates and The Cabin, as well as the intermediate maps Adora's Temple, Balance, Spring Spring, and Moon Landing, do not have removable obstacles and therefore do not work for this achievement.