PSEUDAELURUS VS. ARCHAEOINDRIS
Now let us look at Archaeoindrus: a gorilla-sized lemur with a robust skeleton and long arms. The only species found thus far, Archaeoindrus fontoynontii, weighed around 160 kg and was likely arboreal (tree-dwelling), feasting on leaves and the occasional piece of fruit and seeds plucked from nearby tree branches.
I think a small species of Pseudaelurus wouldn't bother A. fontoynontii. But if this hypothetical battle involves a larger, cougar-sized P. quadridentatus (and this may be the case given its higher seeding), then our giant lemur may be in for some trouble. I'm giving this fight to Pseudaelurus, assuming it can clamp its jaws down on Archaeoindrus's neck before batted away by those long arms.
DIMETRODON VS. AEGYPTOPITHECUS
Aegyptopithecus (known from one species, A. zeuxis), was a small (50-90 cm) ancient primate from the Oligocene of Egypt. The shape and position of its humerus (upper arm bone) suggests that rather than swinging through trees, Aegyptopithecus used all four limbs to climb through branches and along tree trunks.
Sorry Aegyptopithecus, you don't stand a chance against Dimetrodon! The only way it could survive a direct confrontation would be for it to use its cunning, agility, and small size to run circles around Dimetrodon and flee, thereby forfeiting the battle and automatically losing.
HOMO FLORIENSIS VS. PALAEOLOXODON
Palaeoloxodon was a genus of ancient elephants that lived throughout Europe and Asia during the Pleistocene and Holocene. They had long, straight tusks that could grow up to 9 metres in length (depending on the species). One species of Asian Palaeoloxodon, P. namadicus, was around 4 to 5 metres tall at the shoulder, and was possibly the largest land mammal to have ever lived. It is thought that most of the Palaeoloxodon species went extinct due to the introduction of predatory species, including Homo heidelbergensis and other early humans.
Palaeoloxodon seems to have been hunted to extinction by various species of Homo across the globe. And H. floriensis probably knew how to hunt the dwarf elephants of Flores. But if this battle is between H. floriensis and a local species of Palaeoloxodon -- the gigantic P. namadicus -- my bet is on Palaeoloxodon to trample its enemy and win.
UPDATE: I was informed that the species of Palaeoloxodon taking part in the battle is the dwarf Palaeoloxodon falconeri! So my pick is actually for H. floriensis to win this one.
AMEBELODON VS. DEINOGALERIX
Deinogalerix was a Miocene gymnure, a rat-like 'giant' hedgehog, which lived on islands off the coast of Italy. It was an ancestor of modern day moonrats and hedgehogs, and like modern moonrats, did not have quills. Measuring around 60 cm in length, and with a mouth full of sharp teeth, it likely fed on insects, small reptiles, and other small mammals.
I suppose that Deinogalerix could annoy Amebelodon enough that it quits the field of battle, but I think it's more likely that Amebelodon will accidentally step on and squish our hairy-protohedgehog contender.