Use Dartling Gunners as the main source of popping power and support them with support-oriented towers. Play more games in order to speed up the progress of the achievement, as Rounds 81+ contribute less to the achievement than previous rounds, as Super Ceramics contribute less pops.
Tips
Simply use Dartling Gunners as your main source of popping power. Add a buffing hero nearby the Dartlings, preferably Gwendolin or Pat Fusty.
It is easier to simply play multiple games to reach quicker progress to the achievement, as Super Ceramics do not increase the progress count as quickly.
To reach this achievement sooner, add Gwendolin with Dartling Gunners, as she provides Dartling Gunners with a regular pierce buff every so often as long as she attacks, covering the low pierce weakness of most Dartling Gunners. Adding Pat Fusty is also useful with Dartling Gunners, as his Rallying Roar ability increases the damage output of multiple Dartling Gunners within range by a large margin.
Hydra Rocket Pods covers the Dartling Gunner's low pierce weakness quite well; spamming those towers will help reach the 1,000,000 pop threshold sooner. Add Monkey Commerce nearby to save even more money when attempting to spam in Hydra Rocket Pods.
Trivia
The achievement's name and icon are a reference to the Dartling Gunner's unlock process in BTD6. When Dartling Gunner was first added to BTD6, players had to first pop 1 million Bloons to open a gift box and unlock him.
Bloon Science·Gimme that!·Extortionist·Sweet Revenge·Best Served Cold·Guardian·Epic Defender·Defender·You Shall Not Pass·Attack Run·Dark Dirigible Titan
City Honor
Red City Honor·Blue City Honor·Green City Honor·Yellow City Honor·Pink City Honor·Black City Honor·White City Honor·Zebra City Honor·Rainbow City Honor·Ceramic City Honor·MOAB City Honor·BFB City Honor·ZOMG City Honor
Heating up·Afraid of no ghost·Broken Bones·Drill Bits·Top of the heap·That's a wrap·Breaking out·Fires of Mount Bloon
Blops
Blop Around the Clock·Blop Til You Drop
Medals
Poppin' and Bloppin'·Bronze Master·Silver Master·Gold Master·Diamond Master
Powerset Badges
Mixing It Up·The Art of Dart·Rang-ler·Rang-ler·Ready to Explode·Believe In Magic·Watch Me Whip·Bullet Hail·Dangerous Downpour
Epic Powers
Epic Avenger·I Feel Epic·There Can Be Only One (BSM2 Mobile)
Crate Powerups
Full Power·Power Couple·The Power of Money·Powering Up
Research & Upgrades
Power Core·Symmetry·Jack of all Trades·Reach for the Stars·R and D·Tagging Along
Hidden Achievements
Allies Assemble·Big Spender·Breaking Wind·Can't Hide From Me·Getting Crowded·Heavy Lifting·I'm So Dizzy·Look! No Hands!·Monkey Mastery (BSM2 Mobile)·Organized Chaos·Precision·Rise and Shine·Sink the Sub·Skull-diggery