I speculate that this has an effect on how ... tentative predators can
be. Again, wait ... what? I've watched a number of nature videos, and
there is often a lot of backing and filling and trying to get behind
the prey before making the big rush.
Your instinct to think about humans was the right one even though you don't want to consider humans particularly.
What do humans have that only a handful of other animals do?
Ranged weapons like bows and arrows, slings and rocks, and atlatl to throw spears.
The answer, I think, comes from baseball and not zoology, as I explain below.
@Peufeu notes several animals that use bio-projectiles (spit or glue or spider silk), and another class of bio-projectiles could be numerous disposable spores or spines that could be hurled at prey.
Another bio-projectile would be poisonous feces dropped by a bird (or better yet a whole flock of birds since birds in flocks tend to poop in unison at roughly the same target) from the air on you. Poisonous or caustic or acidic poop from a whole flock of carnivorous killer pigeons at once is something you have to take seriously. It would be the moral equivalent of napalm.
The other option is tool use.
Quite a few animals use tools (a few even turn other animals into zombies to do their bidding for them), rather than actually attacking with parts of their bodies.
Tool users, especially those that attack at range, can afford to be psychologically much less tentative because they aren't putting themselves at risk.
Is this far fetched for a much more primitive animal than man?
For example, have you ever had a squirrel throw acorns at you? If you haven't, I absolute assure you that the do it, ruthlessly, with impunity, from high in a tree where you can't get them. They do it to dogs too (something I rather admire them for doing).
Suppose that your velocikangaroo, rather than using his tail like a mace, used its tail which had a sling-like pouch at the end of it, like a baseball pitcher to throw medium sized rocks at prey at 200 miles per hour at distances of 100 feet with deadly accuracy. Now that is a predator who might not be timid at all, and that predator, unlike those who used bio-projectiles, wouldn't have to pay much of a biological/energy supply/healing cost to gather up unmodified medium sized rocks to stack up and throw at prey. Thus, the velocikangaroo could be a tool user simply by throwing ordinary, easy to find rocks, without being a tool maker, which is a much more sophisticated thing.
You'd also want to give your velocikangaroo kean, stereo hearing to locate threats and prey before they go to close and accurately aim at them, and keen binocular eyes to aim with, and a good sense of smell (again to prevent ambush attacks). Color vision might be unnecessary for an obligate carnivore since color vision can actually make it harder to see camouflage and the purpose color vision evolve for (distinguishing ripe from not ripe or rotten fruit) isn't important to a carnivore.
Finally, he'd still have to be pretty fast because if he ran out of ammo he'd probably want to run like hell.