Reading through the forum, it appears like some clan are relatively soft counters to other clans (or bad match ups).

I'm going to try and make my wife try the crab clan (She doesn't like attacking, like resilient things etc.) but I was wondering which clan should I not pick if I don't want to destroy her all the time? Also, what has a bad match up against crab?

I hear that Scorps maul crabs pretty effectively.

Scorpion with their event cancel, strong political skill and attachment stealing is pretty tough for the Crab. Crab want to control the board so having things like Assassination and Way Of The Crab cancelled is really damaging. Also having their Watch Commander Stolen is pretty rough. By the same token Crane is pretty tough since they run their honor up and have lots of cancels. The worst match up for Crab IMO is Crane splashing Scorpion. Crane is worse because they are actively honoring themselves so the natural honor pressure that the Crab card pool puts out can be effectively canceled if you don't play smart to counter act it. The Scorpion match up can be a little easier because they spend their honor a lot meaning they naturally start running their honor down, which helps Crab in the long game (their stronghold slows this attrition, but if played well Crab can definitely speed it back up again).

As to what clans have a hard time with Crab I think Phoenix can have a challenge because they tend to want to have a board populated by synergistic characters and if Crab is attritioning down their board that can take a lot of the wind out of their sails. Dragon also likes to run narrow/tall boards so character removal for them can be pretty devastating. Unicorn currently is considered slightly under the power curve so that might help even the playing field. A Lion deck built to care about it's honor can also have a rough time with Crab pushing down their honor scores and Crab can out draw the Lion.