Karin's best finisher when blocked in A3?

What’s her best finisher move when blocked? I used her slide kick but I get sweeped. I haven’t tried her hop kick but im pretty sure I’ll get the same results. Any tips?

In general, you shouldn’t be going into rekkas without hit confirming the LK’s first. Throw out the LKs, go into rekkas on hit, and mixups on block (walk up, and throw, command throw, more c.LKs, etc).
If you do go into rekkas on block, then its up to you to mix it up, trying to beat what the opponent will do. Since you can end with an overhead, a low, a high counter, a low counter, or the elbows, or even nothing at all, you do have some options. If they’re just mashing sweep, the overhead and low counters will beat them clean. I can’t figure out frame advantage on block from the ‘all about’ guide since I cant read japanese, but I’d recommend either try to practice with a buddy using the different moves and seeing for yourself which has the least exposure on block, and focus during the match on #1 not doing rekkas except on hit, and #2 predicting the opponents response and throw out the answer for it if it is blocked.