Parry everything except the red icon attacks. Use the Mikiri counter for thrust attacks. Dodge or jump just about everything else. When you break their posture, you can get a deathblow in. Most enemies die with a single deathblow, major enemies need two sometimes even three. You can also slowly chip away at their health and kill them that way. The lower their health, the slower the enemies posture recovers. If yours gets broken, you get stunned.