"František has a wife even worse than Matěj."
Translation:František má ještě horší manželku než Matěj.
If you really think that adding WHO IS after wife will alter the meaning, it means that František's wife is worse than Matej himself, not than Majej's wife. One must ask the author of the Czech sentence which one they meant, Matej or his wife. As I said before, the original sentences, in either language, say that František's wife if worse than Matej. I am certain about the English version, but my Czech is inadequate to determine the meaning of the Czech translation.