No, it's not, because technically, Ungarmax and Highwind are better than Omnislash.
OMNISLASH:
Clash! clash! clash! Clash! clash! clash! Clash! clash! clash! clash! Clash! clash! clash! Clash! Ziuuuuuuuuung---BARABOOM-SWISCH!!! (15)
UNGARMAX:
Da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da-da! (30)
HIGHWIND:
Bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom...
Bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom-bom...
Bom-bom-bom-bom! (34)
At least that's the way I see it; but Omnislash is maxed out MUCH sooner, hence its reputation.
Catastrophe sucks compared to Ungarmax, btw.