The first said zord to be a bit bigger than the other zords, it got more fan fare than the others in the beginning.
Ryuuseioh/Red Dragon Thunderzord (Dairanger/MMPR)
First Ranger's zord to go from animal to robo. It was pretty much the spine of Dairenoh/Thunder Megazord.
God Saurder (Kakuranger)/Ape Zord (MMPR)
The red one was slightly bigger than the others.
Red Puncher/Red BattleZord (Ohranger/Zeo)
Other than the 2 zords each Zeo Ranger got a zord, the Red Ranger got his own big old zord.
V-Rex/Q-Rex (Timeranger/Time Force)
Technically not the main Red Ranger, but Time Fire/Quantum Ranger is considered a Red Ranger and his zord was freaking big and became a Megazord.
Gao Lion and Gao Falcon / Lion Zord and Falcon Zord (Wild Force/Gaoranger)
The Lion Zord wasn't always big but thanks to some special food, it got real big for GaoKenTaurus/Pegasus Megazord. And the Falcon was pretty big.
Tyranno (Abaranger/Dino Thunder)
Tyranno was a bit bigger than the other Dinos. It made up the torso, legs, head and one arm!
MaxOhja/Mezadon Megazord (Abaranger/Dino Thunder)
AbareMax/Triassic Ranger was just a power up of the Red Ranger, but he had a big old red zord of his own.
FireKaizer/Centaurus Phoenix Zord and SaintKaizer/Phoenix Unizord (Magiranger/Mystic Force)
Not technically one zord, but the Red Ranger did technically get to have his own robo without the others. He would become the Phoenix and merge with a horse (Valkyrion/Catastros or Unikirion/Bright Star).