| Diffusion Beam
R.O.B using Diffusion Beam
||R.O.B. shoots lasers out of his eyes for a long duration.
The Diffusion Beam (拡散ロボビーム Kakusan Robobīmu, Diffusion Robo Beam) is R.O.B.'s Final Smash. R.O.B. gains invincibility and shoots medium ranged whirling lasers out of his eyes (with almost no knockback), followed by some hard-hitting short lasers (with tremendous knockback). Similar to the Superspicy Curry. R.O.B. can move freely during the Final Smash. Being in the general area in front of R.O.B. causes damage that rises at a 2% damage rate and as long as R.O.B. is in front of an enemy, he will continue doing damage. With the laser having good reach in front of R.O.B, in combination with the hitbox being continuous, lasting for a long time for a Final Smash, and R.O.B. being free to move and pursue his opponents, it is often considered one of the most difficult Final Smashes to evade. R.O.B's ability to move during it results in some chaos as he chases opponents around the stage, trying to catch them in the deadly vortex of his eye beams.
Diffusion Beam trophy in Brawl
He can also use his entire moveset (excluding Robo Beam) during the Final Smash, and can even use items and taunts without affecting its hitboxes.
 Trophy Description
R.O.B.'s Final Smash. He emits a beam from his eyes that spreads across the spectrum and undulates in great variety as it travels. What makes this technique different is R.O.B.'s ability to move while using it. This allows him to use it in combination with his other moves to increase his Final Smash's effectiveness.
- For unclarified reasons, this Final Smash was not described on the Smash Bros. DOJO!!, making this the only Final Smash that wasn't covered by the DOJO!!
- R.O.B. is the only character besides Jigglypuff who can benefit from the Bridge of Eldin Final Smash glitch, giving him a never ending Diffusion Beam (Jigglypuff's makes it remain huge). Although, in order to make this happen, the player must have R.O.B. get caught in the re-materialization of the Bridge during the close-up animation that starts the beam. If the player does it at any other time, R.O.B. will merely take damage and waste the time of the Final Smash. Strangely, if the player uses it right as the bridge becomes solid, R.O.B. will be invincible and will make the noise of the Diffusion Beam, although R.O.B. is not using the move. However, using his down special move will make part of the beam reappear, which will be harmless. Using the Gyro again will bring the beam back. If R.O.B. enters the Negative Zone with Infinite Diffusion Beam, he will take damage and suffer the Negative Zone's effects. If the Zone ends with R.O.B. sleeping, R.O.B. will remain sleeping for an unusually long time.
- Even though R.O.B. can grab and use items during this state, he cannot use items that activate on contact (i.e. Starman).
- Because the lasers are emitted from R.O.B.'s eyes, they point in whichever direction his head is facing. This makes it possible to hit crouching enemies by also crouching, or hitting enemies above by using his side taunt (which makes him look upwards).
- The only Final Smashes (and quite possibly, the only attacks) that can damage R.O.B. during his Final smash are Luigi's Negative Zone and Jigglypuff's Puff Up (during the shrinking part).
- Diffusion Beam is not only the most damaging Final Smash in Brawl, but the most damaging attack in the entire series. When all hits connect in a single character, the Final Smash can rack between 270% and 300%, because the long duration of the move. However, to make the other(s) take the full damage, R.O.B. must grab the opponent right before the hard-hitting beam lands, which is very hard. However, it's possible to make it land when the opponent is grabbed without taking knockback, like if the character autoreleases. Precise timing is crucial in order to deal Diffusion Beam's full damage.