When activated, R.O.B. transforms into a laser cannon and fires a series of small lasers that home in on opponents that are close enough to him. He will then unleash a green laser that can have its angle controlled. That laser eventually becomes massive (about the size of Samus'Zero Laser) for about a second to do a large amount of damage.
Trivia
This is the first of R.O.B's Final Smashes not to have the name "Diffusion" in it.
If Guided Robo Beam is used on 14 Ice Climbers, the beam will glitch out and become invisible.