There are contacts/Lead that exist both in SFDC and Marketo, courtesy the sync. We want few of them to delete from Marketo but we still want them to keep in SFDC without they coming back in Marketo through the sync again. Is this possible ??
Yes this is feasible, with a sync filter. Pay attention though on how you manage the "sync stop" and the deletion, It has to be done from Marketo, and not from SFDC. This post will tell you more on this.