You got to have in mind that this random sumo guy supposedly has done a feat that yujiro couldnt. Of course japanese and their double or triple meaning phrases dont help , but if you remember when obama meets yujiro and asks him if he can turn charcoal into diamond , he says something along the lines of "thats not something a human can do". Now , does that mean he calls himself a creature? So since he isnt human, he can do it ? We do know that at the end of father vs son, yujiro told everyone baki was the strongest human, because he himself was the strongest creature.
Sumo guy can also turn a huge rock of charchoal into diamond so maybe he can put a finger on yujiro ? Not beat thats too much.
Also we Sukune has more explosive power than Baki , and Baki beat Oliver in raw strenght so its not a suprise he is getting man handled