How do I show correct answer in matching knowledge check after failed attempt?

Thanks to everyone for their suggestions, I'll give them both a go and see which fits best for this lesson. I think the second slide would end up looking the best in this case, as the lesson is going to be fairly long and going all the way back with a review might not be a great experience for the students.

Correct answer will be visible in Review mode.  It shows the given and correct answers, but that Review status will only appear after the quiz is completed, by using the Review button on the score slide.

Another approach would be to replace the Feedback Failure message by an image. But it would not take into account the shuffling of course.  But that would be the same with the proposal of the other user (extra slide) which is in my vision an old technique which I don't like anymore, because you'll need a lot of advanced actions to avoid that extra slide when it shouldn't be visited.

I would suggest to create a slide with the correct answer. In that case you can also change the layout of the slide, for example having two boxes for the two categories. In the Quiz Settings you can change the action "on succes" to jump to the next slide of your project, and the action for last attempt would be to jump to the slide with the correct answer.