This is ridiculous. Let's assume that he can't even just turn them into trees (he can, for at least Superman and J'onn...and most likely Diana as well).
He first phases into a different dimension to avoid detection. He then floods GL with all the memories of the entire human race. Concentration gone, hello cologne-bones.
Superman's a rose petal before he can even think, unless they start amazingly close. Remember, all he has to do is think about it and it happens.
As for the other two, converting them into sound waves, BFR'ing them to a different dimension, turning them into trees, or simply growing himself to the size of a mountain and donkey-thumping them. Any would work, and are all things he's done before.
He's also telekinetically held Italy in place while the Earth spun on its axis. techincally, he could just "use the Force" to hold them in place while he decided what to do with them.
Speedblitz scenario, it depends how close they start to him, and if they're smart enough to go for the kill.
Otherwise, they're screwed nine ways from Tuesday.
And whirly, quit playing devil's advocate. Doctor can think Kal into a tree well before Kal would ever try T-Vo.