When I play a 4 cost spell and my enemy plays Defy, does it still count for Jhin Virtuoso and can I banish it?

No, you cannot banish the spell with Virtuoso's ability if it has been countered by Defy.

According to Rule 425.1.b, a card that is countered is not considered to have been "played." Because Virtuoso's ability triggers only when you "play a spell," a countered spell fails to meet the required condition for the ability to trigger.

Furthermore, per Rule 425.1.a, a countered spell is immediately cleared from the chain. Since the spell is no longer on the chain, it cannot be targeted or banished by Virtuoso’s effect even if the trigger condition were met.

Summary of the Sequence

1. Playing the Spell: You play a spell and pay its costs. It is placed on the chain as a Finalized Chain Item.
2. Reaction: Your opponent plays Defy to counter your spell.
3. Resolution: The counter resolves, and your spell is cleared from the chain.
4. Trigger Check: Because the spell was countered, it is not considered to have been "played" for the purpose of triggering "When you play a spell" effects. Consequently, Virtuoso's ability does not trigger.

(Note: While the spell is not "played" for trigger purposes, per Rules FAQ Clarification 2026-04-29, the energy you spent remains considered "spent" for the purposes of other requirements in the game, such as playing Jhin, Meticulous Killer for an alternative cost.)