Tyrantrum
- Strong Jaw is a good Ability
- Brutal Attack and decent Defense
- Learns moves like Earthquake, Dragon Claw, Stone Edge, Crunch, and Play Rough
- Wide and colourful movepool
- Rock and Dragon cover quite a bit at least neutrally
- Other defenses are lacking
- Slow
Groudon
- A mere three weaknesses
- Astounding stats all around
- Learns things like Earthquake, Precipice Blades, Hammer Arm, Fire/Thunder Punch, and Shadow Claw
- Ground is a really good offensive type
- It's a BST 670 legendary
- Can be hard to get
- Shallower movepool than Tyrantrum
Go with Groudon. It has far better stats, and it punches holes in a lot of things.
Groudon @ anything
Ability: Drought
- Earthquake / Precipice Blades
- Stone Edge
- Bulk Up / Swords Dance
- Any halfway decent attack
Hope I helped!