If my opponent has no Weakness and I use Meowstic's "Perplexing Eyes" attack, will I do extra damage on my next turn due to Weakness?
If a Pokemon has no Weakness printed on the card, Perplexing Eyes will give that Pokemon a x2 Weakness to Psychic.
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02), TPCi Rules Team (2019-05-16)

Relevant cards

Note: All applicable cards may not be listed below.
SM10_80
SM10_80