Earthquake is useful, but I wouldn't define that as threatening. When measuring usefulness of a move, you have to take into account how effective it is - kinda like the whole tier power vs use argument.
And Earthquake certainly gets boned mechanic-wise: it has no extra effect besides hitting all these threatening Digging Leafons twice as hard, there's a special trait that makes stuff immune to it and it's on somewhat common Pokemon, and while its type coverage is nice, the fact that it has an immunity negates it.
Draco Meteor gets my vote. The only thing that comes close to it (Outrage) isn't on your list. Nothing is absolutely immune to it, and only one type resists it. That type happens to stereotypically have somewhat low SpDef.
The fact that a Pokemon with a gap of ~50 base between Attack and Special Attack (Garchomp) can use Draco Meteor effectively to hurt its counters kinda proves how unbalanced this move and Dragon in general is. The fact that Outrage is used despite it having such a huge drawback is also a sign.
Also Close Combat is pretty broken mechanic-wise imo. A sweeper-oriented move that is about flawless number-wise (I can't really think of anything with 120 power, 100% accuracy besides the recoil-carrying Double-Edge-like moves and things like Fire Blast), and then has a "negative" drawback that is hardly noticed when you are KOing stuff...