I think a better question would be who's the last team to go ham on free agency and win the super bowl. You could say Seattle did it last year, but it helps that they have a franchise QB, a DPOY candidate at CB, and two pro bowl caliber safeties all making rookie money. Makes it a little easier to load up.
Besides them, who? And don't mention teams that just GOT to the super bowl, because that's not enough for most on this board. You have to win it or you're a failure. So tell me the last team that has been super aggressive in free agency and won the super bowl.
This is not to say that being aggressive is bad or trying to add significant pieces is bad. But to say that without that there's no way the team makes it to or wins the super bowl is being disingenuous to recent history.