As Terran
Make:
Ghost
Marauder
LiberatorSnipe, slow, and air zones beat Ultra durability.
Open in the counter tool with Ultralisk tagged ->As Protoss
Make:
Immortal
Archon
Void RayImmortal and air damage trade better than Zealot-heavy armies.
Open in the counter tool with Ultralisk tagged ->As Zerg
Make:
Lurker
Brood Lord
InfestorKeep Ultras from reaching fragile units with zones and spells.
Open in the counter tool with Ultralisk tagged ->
Zergling
Baneling
Roach
Ravager
Queen
Hydralisk
Mutalisk
Corruptor
Overlord