You choose which opponent or opposing planeswalker Ragavan is attacking as you create the token. It doesn't have to be the same player or planeswalker Kari Zev is attacking.

Although Ragavan is attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example).

The delayed triggered ability that exiles Ragavan triggers at end of combat even if Kari Zev is no longer on the battlefield.