Do not mess with Post-CoIE Krypto. He will bury your ass at the Earth's core.
Pre-CoIE Krypto was a lovable, fun canine parallel to his master, Superboy. He was just as much the good and kind Star-Moses that his humanoid pal was except that Krypto could spend all his spare time on an asteroid licking his own super-testicles. Superboy could too, if he wanted, except he never indulged because of the knowledge that those damnable voyeuristic Legionaires were always watching him 24/7 on their Time Scope Televisors doing "research".
New Krypto is different from his Silver Age counterpart. The new version doesn't have human-level intelligence, can't travel through time under his own power and isn't telepathic. He's just a dog. A smart dog but still just a mutt, and an insanely powerful one. It's funny that Batman is all concerned about the hidden evil agendas of the New Supergirl, but is not at all worried about the natural inclinations of an uncontrollable super-powered dog. Without even knowing he's being a bad dog, Krypto could make the entire planet a urine-stained wasteland*. Batman can be a little short-sighted on occasion.
Sure, Supergirl could conquer the Earth in a day but New Krypto would treat the world as his backyard. While SA Krypto would create the occasional mess from innocent playfullness as he did in his first appearance in 1955's Adventure Comics #210, New Krypto is Grim n' Gritty and has none of the Silver Age innocence about him. He would be a force of nature and cause recurring disasters on a planetary scale. Digging miles-wide holes, de-populating entire ranges of forestland wildlife for a snack, lighting fires and freezing oceans. That's far more frightening than a coup by an alien mall rat with ADD.
New Krypto is the ultimate Alpha Dog. Every other mutt on earth is by default a subordinate member of his pack. New Krypto probably has thousands of litters spread all over the Earth and is surely fathering an army of genetically superior, super-powered puppies that can not be stopped by rolled-up newspapers.
I'd like to see a Krypto: Force of Nature mini-series by DC where in each issue a different hero or team of heroes attempts to reign-in an out of control Krypto wreaking havoc. Understand, I don't want Krypto to be mind-controlled to be evil or poisoned by Red Kryptonite or anything. I just want him to just be a natural, poorly-trained dog that isn't properly housebroken. That would be best. The series would have to guest-star Superman eventually but the following characters would be required at the very least:
- Green Arrow (He originally found an amnesiac SA Krypto in the 70's.)
- Animal Man
- Swamp Thing
- Myxyzptlk (Krypto hates Myxy.)
- Supergirl (One or two panels at most. She needs to get bitten then never heard from again or die of Space Rabies, whichever.)
- Batman (Bats would do something stupid like lasso Krypto with a bat-rope and then Krypto would fly away and drag him across 5 states before dumping him.)
- Plastic Man (Dogs like chew toys.)
- Martian Manhunter (Jonn could shapeshift into a female dog, because we all know how Jonn likes the inter-species stuff.)
- Rex, the Wonder Dog (Rex could be Krypto's sensei.)
- Detective Chimp (Can't have an animal-themed book without the Chimp!)
- Fate (Cameo only, as Krypto digs up old smelly things and rolls around in them.)
- Ch'p (A rebooted Don Newton-style Ch'p, not the toon version.)
- Superboy Prime (Krypto's Revenge!)
* aka: Maryland