Cris "Cyborg" Justino was quick to congratulate Ronda Rousey after she won the WWE Raw Women's Championship on Sunday ... but not without reminding her who's the "most feared" woman alive.

"Congratulations to the Baddest Woman On The Planet for winning your first of many @wwe championship belt

Sincerely,

The Most Feared Woman On The Planet."

Cyborg has been trying to get a fight with Ronda for years -- but it never happened. Cyborg previously accused Ronda of ducking her.

There's been talk of the two facing off in WWE down the line -- with Mick Foley even trying to convince Vince McMahon to sign her.