If you just want to figure out who is the actual most powerful, not just make a list of all the candidates, I would say it has to come down to a contest between the Q and the Douwd. None of the others have demonstrated any ability to actually eliminate entire races/planets/whatever simply by "wanting" to. And by just ONE of their "individuals," wanting to. A single Borg can't do much of anything, by itself.

The Organians could but they found violence and interfering with other (less developed)species distasteful,but they were able to make all the weapons of Starfleet and The Klingons useless(not only on the Enterprise and the Klingon space ships around Organia but the space ships everywhere).

The Borg wouldn't be in the discussion. And we don't know enough about the Traveler's powers beyond that his race can manipulate space-time to some degree and are very attracted to young boys. So I guess I'll go with the Pakleds. They are smart. They make things go.

@Nexus71 said:

The Organians could but they found violence and interfering with other (less developed)species distasteful,but they were able to make all the weapons of Starfleet and The Klingons useless(not only on the Enterprise and the Klingon space ships around Organia but the space ships everywhere).

The Organians could apparently make individuals - such as Klingons guarding cells - phase out or something so they didn't know their prisoners were escaping. But there was no evidence that the Organians could make entire planets or species cease to exist - or never evolve in the first place - as seemed to be the case with the Q and certainly with the Douwd.

Star Trek: The 15 Strongest Species, Ranked From Weakest To Most Powerful.

They left quite a few powerful out of this list and shouldn't the Jem'Had ar and the Shapeshifters just be The Dominion both without each other wouldn't be much of a threat.

Good point, since the Founders created the Jem'Hadar and control them with "the White" (the Founders are RACIST!) and the Founders can't really do much damage by themselves.

Although they did replace General Martok and then used Klingon forces to cause trouble...

Perhaps they replaced the Breen leaders too, and the Dominon-Breen "alliance" was phony from the start.

Just like the US government let "the white" willingly destroy black communities during the 80's and 90's

Even assuming that premise is correct, which is one of the loonier conspiracy theories of the past century, don't "the black communities" have any responsibility for not being addicts etc?

Don't "the black communities" have any responsibility for not shooting each other?

And so on.

Watch the movie "Kill The Messenger" it is based on facts.A investigative reporter was silenced(murdered) for publishing that information.

And yet you're still alive, so it must not be true.

Just watch the movie the reporter did found out a link between the weapons that the US government delivered and getting drugs back return and that drugs being used by the US government to flood the inner cities and black communities in particular.Just read about reporter Gary Webb his book Dark Alliance where he investigates the CIA weapons for drugs program which was part of the Iran -Contra thing it was even part of the Kerry Committee Report.

Please keep this on topic.

Sorry But my point on the Jem'Haddar and the Changeling still stands that upon their own they are not that powerful one could argue that the Vorta is needed as well for them to become the all powerful Dominion.

@Nexus71 said:

Just watch the movie the reporter did found out a link between the weapons that the US government delivered and getting drugs back return and that drugs being used by the US government to flood the inner cities and black communities in particular.Just read about reporter Gary Webb his book Dark Alliance where he investigates the CIA weapons for drugs program which was part of the Iran -Contra thing it was even part of the Kerry Committee Report.

I've heard about that. "Wealth Through Marrying Rich Widows" author Sen. John Kerry was for it, before he was against it.