Reposting/Rewording an old discussion of mine of how
insanely OverPowered Ruby's Semblance is if the writers understood what they'd had done with it. They've made Ruby among the most powerful characters in the story in terms of firepower, but don't understand this, so she's a jobber instead. Let me explain based on an old post I made a while ago.
Ruby's Semblance originally appeared as "super speed" with Rose Petals as a sort of magical byproduct (for aesthetic purposes because Monty's rule of cool methods). This in itself has impressive feats since she created F5 Tornado winds by running, and then dodged the massive food-tornado that was on her tail that she created, easily putting her above 300mph. This is repeated in the V4 Character Short where she uses it to lift a huge Grimm into the air. Then take into account that she bullet timed casually in V1E1 and you get a supersonic to hypersonic character. She even outsped Harriet at one point, which if we go by some wank, is a lightning-level feat.
https://streamable.com/xo8id
All of this pales in comparison to what we later hear from Penny's explanation. In short, Ruby controls matter; Petal Burst is described as disassembling herself at a molecular level. This is a feat comparable to The Flash's higher-tier feats where-in he can make himself and other intangible or stop intangibility (see
https://files.catbox.moe/2kygvl.jpg and
https://files.catbox.moe/p6ngp8.jpg )
As essentially weightless molecules, Ruby can go as fast as she wants in any direction, so long as she keeps control. She could theoretically move at or past the speed of light and pull a Barry Allen (infinite mass punch, time travel, etc.). And we know she's essentially weightless because she effectively flies around even splitting apart into groups of petals (such as against Neo in V8E14) and should be able to negate someone else's intangibility as well.
However Petal Burst actually goes a step ABOVE this; Energy-Matter Conversion and back again.
We see this when she and her friends sneak into the Atlas HQ and whisk past the guards.
In V2E8 Ozpin notes physical, real petals being left behind, meaning Ruby casually creates and dematerializes matter... from 'nothing'. I.E. Energy-Matter conversion (real examples of the opposite include Nuclear Fusion and particle colliders), which means that she theoretically could pull off the same abilities as Overhaul from My Hero Academia, or even make the air around her explode in nuclear fire like Omniman when he massacres that Alien Planet in Invincible S1. This makes Ruby potentially an FTL walking nuke. If Ruby was a bloodlusted psychopath, her Matter-Energy conversion could even be turned in reverse, literally erasing the molecules of someone from existence.
Putting aside that devastating potential, I don't think most people understand why creating "new matter" is so insane. To put it mildly, Conservation of Mass means that matter cannot be destroyed or created (in a closed system) and the same for energy. However \[ \E=mc^2 \] means that by going faster than light you can essentially convert a large amount of energy to a small amount (atomic level) of mass and Ruby does this casually as a side-effect of her powers. For context the Large Hadron Collider takes significant amounts of time and 13 Tera-electron-Volts of power to produce less than 3 Picograms of matter, and requires some protons to do so.
The only real problem with this is how it's depicted; It doesn't explain how she can be struck while incorporeal as a mass of molecules, it's like literally kicking petals but even more futile, they'll just disperse around you. Now in V3 when Mercury does it you can explain it by saying he has Aura and as it's soul against soul, he can strike her aura (kinda like Haki works against Logias in One Piece) but how does the Jabberwalker do it? It has no aura, maybe some Darkness Brother magic bullshit.
TL;DR: Ruby should be able to pull of Flash level feats... but doesn't because bad writing.
https://rwby.fandom.com/wiki/Petal_Burst
>Inb4 Aura limit
That might limit her from keeping up lightspeed but I mean... Jaune -> Supercharge her Aura and watch her go!