Oh yeah, you KNEW Haohmaru would be in the top 10! Heck he's the poster boy in the Samurai Shodown franchise, he first appeared in the original Samurai Shodown and has became one of the most popular characters in SNK history. Heck he even appeared as a guest character in Soul Calibur 6! The reason why I put Haohmaru on this list is his backstory and design.
Let's start with his design, his character origin resembles Miyamoto Musashi, the greatest swordsman in Japan.
Now for his backstory, after being defeated by Jubei at the age of 15 due to his lack of experience, he was brought to Nicotine Caffeine so that he may gain proper training. During his training, he and his former close friend Genjuro fought each other over a prized katana.
Surprisingly Haohmaru won granting him the prized Katana, Fugodoku.
He enjoys the thrill of fighting worthy opponents. He constantly journeys throughout the land in order to improve himself of being the greatest warrior of Japan.