I say the One-Eyed Dragon.
He tends to stalemate Yukimura Sanada while having the advantage in their fights and striking a wee bit of fear within him and this is the same guy who fought Tadakatsu. He beat Keiji Maeda while wounded without any real effort at all. Took a bullet and played it off like he hasn't even been touched for the rest of the day. His movement and reaction speed is insane for the world they live in.
Hmm they might have fought in the last episode. When it's showing everybody at the end after Nobunaga is beaten. But I don't think it shows much of the battle if it shows one at all. I was disappointed in Tadakatsu Honda. I was hoping for somebody cooler, and a rival in power to Date, and Yukimura. Not a mecha type thing.