If the applicant (who was sponsored) renounces his PR, will the sponsor still be responsible for any kind of financial responsibility for the applicant in case he visits again?
If no longer a PR, the applicant will not be eligible for the types of social assistance covered by the sponsorship agreement.
But: this does not remove any financial responsibility the sponsor and applicant may have to one another under civil law (eg marriage/divorce, contractual, any kind). I.e. it would be relevant to the responsibility vis a vis the government.
And of course any assistance that may have been received prior to the renunciation.