Bloons get pushed backwards or slowed after each hit.
~ BTD6 description
Knockback is the first upgrade of Path 3 for the Super Monkey in Bloons TD 6. It adds knockback to every attack, giving the Super Monkey with the capability to push back or slow down bloons on each hit. It will push back bloons besides Leads and Ceramics by 25% backwards, slows down Leads or Ceramics (including their fortified variants) by 60%, or slows down MOABs and above by 30% (except the BAD, which cannot be slowed at all). The knockback effect lasts for 0.1s per hit.
Knockback allows the Super Monkey to inflict knockback effects onto affected bloons, giving defenses more time to destroy the affected bloon(s), especially for the Super Monkey itself. It serves highest value against stronger bloons such as the early Round 40 MOAB.
When looking for reliable sources of knockbacking, it is worth knowing how each of these cross upgrades interact.
3-0-1 Sun Avatar can knockback up to 6 bloons per sunbeam, 3 sunbeams per shot, and at double attack speed. Additionally, it can pop Leads but not Purples (unless Strike Down the False MK is active). It has the default Super Monkey range, though its range could be further increased with the upgrade Ultravision.
0-3-1 Robo Monkey can knockback up to 6 bloons per dart from its 2 separate arm attacks. It can pop Purples but not Leads. It has good range, and it can be further improved with the Ultravision upgrade.
0-0-3 Dark Knight can knockback up to 5 bloons per dark blade, can deal +2 damage to MOAB-class, and it can be crosspathed with other paths for additional benefit, preferably Path 1 with the double attack speed and +2 pierce.
As of Version 12.0, the nerf to the knockback towards Ceramics makes it difficult to stall Super Ceramics in place. In fact, the new knockback effect to Ceramics is now similar to that on MOAB-class bloons.
Dark Knight restores full knockback to Leads, Fortified, and Ceramics, but it is rather difficult to utilize Dark Knight for an intended purpose of stalling Super Ceramics.
Appears to be nerfed in attempt to balance out Path 3 crosspathing, more specifically with Sun Avatar.
Knockback has decreased knockback for Leads, Fortified, and Ceramics (-100% --> -60%). Upgrading to Dark Knight restores the full -100% knockback.
Knockback artwork in the upgrades menu
Knockback Super Monkey
Knockback upgrade icon in upgrades menu
Crosspathing in BTD6 (Top: Path 1, Bottom: Path 2)
Upgrade portrait for Knockback
Upgrade icon for Knockback
Instamonkey icon for Knockback
This upgrade is the only upgrade below Tier-3 that costs exactly $3000 on Medium for the upgrade alone.
The Knockback upgrade is also the most expensive of all Tier 1 upgrades in the game.
This upgrade costs the same as the Super Monkey did in BTDB Mobile since Version 4.6. Likewise in BTD6, Laser Blasts now costs the same as the Super Monkey does in BTD6.