Self-proclaimed "Strongest" swordsmanship. Oden's confidence was not in vain,as he was the only one to inflict a serious wound on kaido.
Oden said this. Look man, Oden sailed with WB and exchanged blows with him, saw Vista and everything, then he was transferred to Roger's ship and even exchanged blows with Roger, saw Roger and WB fight for 3 days, and after that he sailed for a while, 2 years? Side by side with Roger and Rayleigh and arrived in Wano openly saying that his style is the STRONGEST.
It's not me saying this but Oden thinks he's better than Rayleigh and Roger and anyone else you've ever met.