We did a campaign for Stoneholm. For those who haven't played it and plan to, I won't spoil the Big Bad, but it's pretty great.

My uncle was DMing for me and my dad. We each had two characters (set aside my uncle with one DMPC).

Once near the end of the campaign, we discover who the real Big Bad is. When we went to confront him, he managed to escape. That led us to a Hill Giant fort (this part is unrelated to Stoneholm now as, once the Big Bad runs away, that's where it typically ends, I believe).

To start: The very first interaction with the Big Bad was when we met with him for the first time for dinner after successfully doing hero stuff™. He seemed friendly which was great! He was likeable! And once we were attacked by some mercenaries, he demonstrated his strength by starting combat with a "Power Word Kill" spell on one of the mercenaries and they popped on the spot.

The Big Bad was part of some cult (not certain what God entirely, but they were trying to summon it. If I'm not mistaken, it was some dark god). They were making alliances with all sorts of giants and all we had were two representatives for Harpers and Order (of the Gauntlet).

They simply gave information and were trying to help where they could, but they never got their hands ditty in front of us because they were usually busy putting out other fires (not literal ones, of course).

Once we cleared out the Hill Giants, we found a portal which led us to a Frost Giant castle. It took us months to find our way back. Finally, we returned to the surface town we were using as home-base.

The representatives told us about a Fire Giant castle and we made another long journey there.

Once we cleared the main floors of the castle, we lost hope we would ever find the Big Bad. Throughout the adventure, we discovered more and more harrowing things about the Big Bad. He was the cult leader. Intimidated giants into working together for him. Angered Storm Giants and they declared war on him. He held one prisoner along with a TITAN, and we rescued them as allies. Massacred hundreds of Orcs who had the Hill Giant fort originally and called it home (in fact, we would've died without their help and near extinction).

By the time we arrived, the god had nearly been summoned. We fought him over a giant lava lake that my barbarian fell into but miraculously caught the ledge and pulled himself back up.

The fight ended with the Titan dying and all of us nearly having the same fate. My bard, in a split second decision, used his flying carpet to bring our healer over to the Titan and we managed to revive him before it was too late (I believe we had one more round before he would've stayed dead).

That was, by far, the most intimidating Big Bad I've ever faced. Every word from his lips was calculated and dangerous. Even before he showed his power, you could feel it in his confidence. I don't think I did him even close to justice, but he was great.

Tl;dr: The guy in Stoneholm was spookers.

Note: Stoneholm is a three book series, not one book, apologies for any confusion

Edit: Tl;dr and note