In the first appearance of Shazam and the Wizard, Batman is pointing out how Wizards make things more annoying to understand. Given that this universe's take of him has a working relatonship with Constantine, one of the most...understandably hard people to work with, it kinda makes sense.
There is a sort of poetic reason for the Watchtower to be made into a volcano. Who made it? The Brohers Djinn, the same people who busted their original HQ. It's kind of a nice little 'take that' to them.
The fact that Firestorm's first opponents are The Nuclear Family. Who else can go against the Nuclear Man than a small army of androids based around a nuclear fallout?
Just had a realization on how Solomon Grundy can raise the dead. He's a man who has been cursed by a magic swamp, so there are likely voodoo shamans living around there or some other form of necromancy. He could have picked up on those. Plus why he is crafty? He's a mobster, some of his crime planning skills are likely intact somehow thanks to Slaughter Swamp's influences.
In the comics, he's always tough, and always strong, but just how smart he is, and what skills from life he can access, varies from one resurrection to another. Clearly this was one of his brighter periods.
Its revealed in Field Trip that, initially, Firestorm could not make Kryptonite. This makes sense, as Kryptonite is an alien mineral and thus not from Earth. Ronnie Raymond is only a high school student and his mentor, Professor Stein, is a physicist. Neither of them knew what made up Kryptonite and thus cannot make it just out of thin air. They needed to study it first.
Not exactly "fridge", since they more-or-less said that out loud.
When the Justice League is hit with a "Freaky Friday" Flip, Batman suffers the least drawbacks out of everyone while in Stargirl's body; as the League's resident tactician and the one most likely to study his teammates' powers, his Crazy-Prepared mentality made the transition easier.
In the climax of "the Fatal Fare" Swamp Thing takes advantage of the large supplies of water stored within the Apokaliptian war ship. It would make sense that an army the size of the average invasion fleet Apokalips uses to invade the Earth would need a lot of water to sustain itself.
In the short "It's A Trap!", Lex made a bat with Kryptonite chunk. In short, he's a power armor-wearing bat-man, just like Batman is in Batman v Superman: Dawn of Justice. (The entire thing is a dig on the film's battle anyway)
Calythos creating a volcano near Metropolis...in its park at first, at that. That could have done a lot of damage if not for Wonder Woman and Superman.
Let's face it: in the amount of time he had the League under his control, Toyman could have done far, far worse with them than making them fight for his own amusement. Just think about the sixteen hours...
How about the fact that he had the ability to bring in DARKSEID ?!