Now just so everyone know, I've only watched the shows. I've seen every movie and every episode of Inuyasha. But I haven't read the Manga so do not be upset with me if some of my thoughts are different.
I believe that Sesshomaru, at any point in time could have killed Inuyasha. Yes, their father did leave Tenseiga to Sesshomaru and Tetsusaiga to Inuyasha, making it futile for them to fight. But look at everything that happened.
In the early episodes, Sesshomaru used a human arm from Naraku and showed Inuyasha the Wind Scar. He could've easily just used the Wind Scar on Inuyasha.
Main Characters: Miroku, Shippo, Kagome, Sango, Kirara and InuYasha.
Many of the fan letters I receive ask the question “How old are Inuyasha and the other characters?” Some fans make guesses. The character with the greatest range is Miroku, with guesses ranging from the late teens to late twenties… I basically think it's all right for the readers to view the characters as whatever age they see fit, but since so many people ask this, I'll answer with the ages I have in my head as I work.
It is clearly stated that Kagome's age is 15, so for balance, Sango is about 15 or 16, and Miroku about 17, 18. I think of Kikyo as having died at about age 17… Demons...