Imo the scariest are typically the enablers that limit interaction. For example a Master Transmuter is terrifying if it doesn't have summoning sickness and the opponent has multiple cards in hand.
What you're describing although would likely fall in a category of hard-to-deal with threats. Old Eldrazi titans are typical, indestructible + trample on blightsteel colossus are good for surviving various removal, void winnower is good at stopping half(ish) of the board wipes and removal. If your grabbing multiple creatures with one spell (like with mass polymorph/indomitable creativity) then haste enablers like dragonlord kolaghan are good.
What you're describing although would likely fall in a category of hard-to-deal with threats. Old Eldrazi titans are typical, indestructible + trample on blightsteel colossus are good for surviving various removal, void winnower is good at stopping half(ish) of the board wipes and removal. If your grabbing multiple creatures with one spell (like with mass polymorph/indomitable creativity) then haste enablers like dragonlord kolaghan are good.
Links to my most current deck lists;
Primary EDH; Rakka Mar Token Perfection, Crosis Mnemonic Betrayal, Cromat Villainous, Judith Gravestorm, Rakdos Empty Storm, Exava Artifacts, Bant Trash, & Fumiko Voltron!
EDH kept at home; Ruzzian Isset & Rakdos LoR!
EDH (nostalgic/pimp/retired) in storage;
Latulla Burns, Akroma Smash, Jeska Voltron, Rakdos Storm, Bladewing Darghans, Lyzolda Worldgorger, Xantcha Steals your Heart, Jori Storm, Wydwen Permission, Gwendlyn Paradox, Jeleva Warps, & Sigarda Brick!
Legacy Showanimator and High Tide!