I havent read such a bad thread in a while. Big Mom hasnt got any buildup remotely close to Blackbeard. She wasnt the main villain even in her own arc, WCI. Meanwhile, Kidd and Law were created on a whim, who arent supposed to have a role in the core story. Thats why Oda grouped them together (Big Mom - Kidd - Law) and got rid of them from the story.
Blackbeard's buildup started since Jaya and his buildup isnt like any other antagonists in the series. If you think about it, Blackbeard and his group are the only villains whose powerlevel isnt static. All other villains, Kaido, Big Mom, Akainu, Gorosei, etc, are already at their peak. Meanwhile, Blackbeard crew have been growing in parallel with the strawhats. You think Oda is building such a special crew for Kidd/Law/Katakuri/Yamato - whose role in the story is complete?
This is the only crew that perfectly mirrors the strawhats. Blackbeard is a coward, ambitious and cunning D - the complete opposite of Luffy which has been highlighted since their intro at Jaya. He has his own swordsman who happens to fight without honor - has a fruit for cheap shotting people. He also has a female member who is cruel and ugly - the complete opposite to kind and beautiful Nami, has his own doctor who can afflict others diseases, has his own sniper who is calm and collected etc. No other organization is tailor made for strawhats this way, be it pirates, marines, or Imu-gorosei.
Blackbeard is just too important:
- This is a pirate manga and Blackbeard is the most famous real life pirate of all time
- Oda's favorite real life pirate also happens to be Blackbeard
- If Oda could join a pirate crew in One Piece verse, it would be the Blackbeard crew
You have to be completely delusional to think anyone else other than strawhats can take them down.