Somewhat unintuitive, if you're diagonal or an L-shaped distance away from an opponent and you're both using H-slash, you both take damage and nothing else happens - which can lead to a stubborn game of seeing who chickens out first.
If clashing on those diagonals isn't feasible the way in-line ones are, have an H-slash "clash" maybe push both players back by 1 without stun so they're forced to reconsider their attack vector.