Nashville IMO, even if they haven't won the Cup yet.
If you're looking strictly at hockey moves, Tampa is probably the best recent example, but they do have the added benefit of no state income tax, and had to go the route of bottoming out to get two franchise players to build around (Stamkos and Hedman), which is a similar story to Pittsburgh. As great of a job as they've done at filling out their roster, when you get something like that with franchise players in consecutive years, it can completely turn your franchise's fortunes around, and in Pittsburgh's case, it did a complete 180 on their reputation.
It's been a slow burn for Nashville for sure, but that can be expected with an expansion team. They didn't catch lightning in a bottle in an early season like the Panthers or Knights, but they stuck through the growing pains with the same GM that has been there for 20 years to build a franchise that has been competitive for the last 15 years, and one of the best and most reliable franchises very recently. They've done so while establishing an identity and culture you can immediately identify with the team regardless of whether they've moved on from their franchise's best players like Weber and Suter, and they've built up a rabid fanbase in a place you wouldn't really expect to take off like it did, slowly working their way up the cap space chain as they can afford to.
You look at their draft history, and the only potential franchise guy (identified off the bat in their draft year) there was Seth Jones, and they traded him before he really broke out. Upshall, Legwand and obviously Suter were higher picks that contributed (Suter obviously to a huge degree), but the rest of that team was more or less built with shrewd signings/trades/draft picks.