Ok so Imma just throw off everything that's in my personal list and not there, sorry if it's already been suggested :
-Stalemate Redux by TehTactiq & TheFrozenTide
-Arctic Arena by Eclipsed & more
-Poltergeist Reborn by Pennutoh (published by ThePrimeEvil)
-The Hell Origin by Stormfly & more
-Cadrega City by Pennutoh
-Athanasia by Viruz
-Wisdom by Zipixbox
-Angelic Blood by Viruz
-Instant Execution by Plexidit & more
-Redemption by AngryBoy & more
-A Darker Fate by Logic & Marwec (published by Combined)
-Hyper Light Drifter by Keyblade
-The Antimatter by Bianox & more
-Leziclub by ScpLanst (published by Sunix)
-Sysmique Locked by Jakerz
-Kinetics by Conra & more
-Paradox Theory by CairoX
-Thirteen by Antares
-Friendship by Delcherro & more (published by Meatius)
-Gammaray by Stardust & more
-Dystopian Disruption by HaydOS & more
-Purgatory by Mactanow
-AlphA by Zelda
-Forgotten Galaxy by TMNGaming & more
-Sheol by RicoLP & Alkali
-The Elysium by Jindotgae & more
Ordered in order of descending difficulty based on my opinion, I'm pretty sure they are all harder than Ultrasonic.