Steely

 is an achievement in Bloons TD5. It is unlocked by popping 250,000 Lead Bloons. This achievement is arguably the hardest to achieve because there are no Lead Bloons in Freeplay Mode and there are very few of them in regular games. In a Hard or Impoppable game you'll see 277 Lead Bloons.

It should be noted that Lead Bloons popped in Sandbox Mode do not count toward the Steely achievement.

Tips

 * Replaying the Wizard Lord Special Mission is a good way to get this achievement, as it has 663 Lead Bloons. This is due to the fact that all Pink Bloons are upgraded to Lead Bloons. If you replay it 5 times a day, you will get the achievement in roughly 2.5 months.
 * Another option is to play the Random Challenge called "Chemical Warfare" over and over again as it contains a lot of Lead Bloons. All Bloons lower than Lead Bloons spawn as Leads. If you have already beaten this Random Challenge then, unfortunately, the only way to access it again is to reset your challenges.
 * Full Steely walkthrough https://www.youtube.com/watch?v=p-5AxXNDX_M

1 - go to Wizard Lord SP Mission

2 - spam dart monkeys

3 - on round 12 start upgrading your DM to 0/3

4 - on round 18 get some camo protection

5 - use the Phoenix on round 23

6 - sell all and set up 2x (4/1 boomerang and 3/x ice tower) + 1/3 glue gunner

7 - I don't know how much time to unlock X% of the achievement. 1 million is 40% OR MORE. So 2.5 million is 100% for sure

8 - finish, save and get your trophy

9 - if using double money you can start the regen farm on round 14 (42 Lead Regen)

Trivia
This is also an achievement in Bloons Monkey City and is unlocked by popping 1,000,000 Lead Bloons.