Well, I'm late to the party, but might as well throw in my two cents
Strength: Garnet is the clear winner here. Borderline Country level vs Country level+. Though, Kenshiro does have an impressive healing factor that has let him walk off extreme beat downs in the past, so it should help him stay in the fight longer.
Speed: Equlized lmao
Abilities: Alright, here we go
Right off the bat, Hokuto Shinken is useless against her since she's made out of hardlight.
So over half his arsenal is now gone.
His other martial arts (Nanto Seiken, Gento Ko Ken, etc) rely on AP to damage his opponent, and Garnet has the durability advantage and her regen is insane (though Ken should be able to copy Souther's Tenshō Jüji Hō, which lets him glide and phase through his oppoent and rip them apart, but her regen likely counters it)
His saving grace here is his two forms of precog and Muso Tensei.
One lets him see a flash of the future of his opponents attacks (like whether or not it'll kill him). Both Raoh (who displayed it in both the manga and anime, though the anime went more in depth with it) and Kasumi Kensiro have been able to use this ability, and Ken's harmonized with Raoh's soul. So, when he see's a future where his head is caved in from on of Garnet's fists, he'll do the smart thing and use Muso Tensei to stay alive.
His other form of precog is where he reads his opponets aura to predict their next move (Ken used it against Raoh in their final battle, and should most definitely have it after observing the Hoktuo Ryuken users).
Muso Tensei also has a history of activating to protect the user without the user consciously doing so. When Kaioh knocked Kenshiro unconscious, and then went to finish him off, Muso Tensei (and Ken awoke the original Hokuto Bloodline) activated and it scared off Kaioh, who was much more powerful then Kenshiro at the time. Kasumi Kenshiro was knocked unconscious by Liu Zongwu, and was about to be killed, but then Muso Tensei activated to save Ken's life, even though he was KO'd.
So basically, if Kenshiro is in serious danger or on his last legs, Muso Tensei will activate automatically to protect him.
Also, couple other abilities that can help him stay alive:
Instinctive Reaction: All Hokuto Shinken users possess the ability to fight and dodge via subconscious reflexes, so well that it can counter other fighting styles that rely on subconscious reflexes. Advanced members can fight with "a blank mind," making it even more difficult to keep up with their movements.
Duplication: Can can and has used his ability to create ki clones to swarm his enemies (like when rushed the advanced demon at the land of asura). He has also used it to throw his enemies off his trail (like when he used it against Kaioh).
Spatial Manipulation: Could help him either dodge fatal blows via warping space around himself (Anryu Tenha is kinda useless here though)
So, Ken should either open with Muso Tensei via precognition and automatic activation, or his regen, instinctive reaction and other abilities listed above should let him stay alive long enough to use it.