The Flash - 'Invincible'

"Bored now."

The Legion of Zoom is on the march, tearing up Central City, but it turns out that the problem with recruiting every meta on the block and killing most of them after one failure is that pretty soon you have a legion of losers, and the newly re-empowered and spiritually invigorated Flash is cleaning them up by the bucket load. Unfortunately, there are a lot of them, so Harry and Cisco begin working on a way to use the variant frequency of Earth-2 matter to build a city-wide stun blaster.

Zoom is working on a plan so fiendish, so diabolical, that he won't even tell his last remaining half-way decent disciple what it is, just that she gets to knock down buildings. Said disciple is Black Siren - the Earth-2 doppelganger of the late Laurel Lance, rocking the Dark Willow look - whose metahuman sonic abilities can not only take down the Flash, but level whole buildings.

As things get worse, Wally steps up to fight, regardless of the risks. Jesse shares his feeling that they ought to be doing something after being hit by dark matter, but Harry channels this into putting her mind to work on the stunner.

With Barry needed to create a sonic barrier that will reflect the blast back on itself at city limits, Cisco and Caitlin have to distract Black Siren by cosplaying at Reverb and Killer Frost. They delay her, but she cottons on fast, and despite a brief display of Reverb's blasting power from Cisco, they are saved only by the stun wave, which drops every meta except Zoom, who flees through a breach.

The gang's celebrations are interrupted, however, when Cisco vibes the destruction of Earth-2, and then Zoom turns up, kidnaps Barry's dad and then murders him in front of Barry in an attempt to prove that they are alike; that witnessing the death of a parent will turn the Flash into another Zoom.

So, that was a lot to drop in an hour, although I suppose the show has to compete with Arrow's Armageddon. Its answer to that gauntlet appears to be Crisis on Some Number, Countable or Otherwise, of Earths, and may bring Supergirl's National City to Earth-1 now that they share a station as well as creators.