Question

Is the Suicune that you face in the first dynamax adventures a guaranteed catch?

Answer 1

All catches from dynamax adventures are garunteed, the suicune included. The hard part is actually defeating them, however.

Source:Experience, and I read a few articles that said that

Comments

However, it's not guaranteed you defeat it.

Answer 2

On your first Dynamax adventure you’ll face off against a Dynamaxed Suicune boss and can capture it during this fight.

Don’t worry if you fail this fight as its location will be recorded and you can try again. You can catch the Suicune easily with any Pokeball as it has a 100% success chance.

Source

Hope this helps! :)