Well, for starters, the weakest of the DT gods (that we have on the wiki so far) has been murdering almost every other High 1-B he's been put against. Badly. The only people who've survived against him were beings who he couldn't kill, and those very same beings were incapable of putting him down as well.
As far as raw power goes, that same god-tier transcends, and is capable of destroying, the entirety of the Dark Tower. The Dark Tower contains all of creation inside of itself, and as explained via a direct novel quote on
Ga's page, "creation" in DT is made up of an infinite number of floors, each of which contains an infinitely-spanning multiverse, in which the mere atoms of a single floor are large enough to contain the entirety of every other floor below it.
Basically, the High 1-B structure of DT is larger and much more complex than the ones found within 90% of the other verses we have listed that reach that high, and the weakest of the series' deities transcends it/is capable of ripping apart the whole thing like it's made of paper. He's also capable of regenerating from the destruction and surviving in the chaos left over from it.
Hax. All of the DT god-tiers have metafictional abilities. The strongest one (Gan) is quite literally the creator of "plot" and "fate" as concepts, while the weakest (The Crimson King) is still capable of opposing him through the sheer potency of his hax powers. The Crimson King's mere speech kills random beings in the multiverse, and he's capable of resisting High 1-B level existence erasure as well as generating shields with his plot manipulation that effectively make it so that attacks simply miss their target. Bessa is the patron saint of gambling, thus giving her complete control over probability. Gan is
transdual, and is capable of outright limiting the power and influence of other beings comparable to himself. (He did this to the Crimson King)
TL;DR? The three of them are stupidly powerful even for their own tier, and have hax that make them largely unkillable while simultaneously giving them many, many ways to destroy their opponents. And they directly scale to each other. With just about everything they have.