The Red-legged Seriema (Cariama cristata) is the closest living bird I can think of to a dromaeosaur foot-claw-wise. The Wildlife World Zoo(thanks Bree for letting us interact with Ellie the Seriema!!!) was super awesome and allowed me to study their seriemas.
Note the "killing claw" equivalent (oversimplifying I know) of a dromaeosaurid (="raptor" of Jurassic Park fame, like Velociraptor), its tip is quite sharp as it is held off of the ground.
Though it walks on all 3 toes the middle and outer claw tips are worn down as they touch the ground. The inner claw, however, is quite sharp as it rarely touched the ground in my observations.
The medial super sharp claw was also more strongly recurved. I watched it manipulate prey items and it used that "killing claw" to "steer" its prey, to hold it down. It preferentially used that claw to hold items that it then used its beak to bite and rip (its beak is hooked).
The keeper advised she hadn't seen it use its claw to kill but had seen it jump-kick and it seemed to be using the claw to slash.
I took hundreds of claw pics (they probably thought I was crazy :-)) and 20 minutes of video. It was super cool to be inside the enclosure!
Some of our friends in Brazil (thank you @direita_sigma ) advised they keep these birds around to keep the poisonous snakes down. Genetics is an amazing thing as Ellie had never seen a snake before yet, lo and behold, when she saw one (even a plastic one such as this) she promptly jumped, hopped, then grabbed it and thwacked it hard to the ground multiple times (bottom blurry pic, I had no idea it was happening as I was shooting through the lens, mea culpa for the lack of sharpness!).
Ellie was extremely inquisitive, so much so that while I was taking her picture she opted to get very close to me and peck at the camera strap.
We included a few pics of her preparing to "strike" at keys (see above). She does the same with mice. You can see the big "killing claw" which she uses to smash down on top of the keys, holding it in place while she then grabbed it with her beak. I observed her move the plastic snake in the same fashion (no good pics though sadly). Bree (our host) advised Ellie seems to use the foot to hold/steer prey.
BYU's Taylor Oswald introduced me to the "ripper"/RPR/Raptor Prey Restraint model that seems to have originated with Fowler et al in 2011 from what I could discern from a brief search (Check out Figure 1). They propose dromaeosaurids would grasp prey and use the "killing claw" to grip it while bodyweight holds it in place, the long tail giving balance with arm-flapping to hold it on top of the prey so it can go to work with its teeth (they go into much more detail, great read btw!).
Seriemas phylogenetically appear to be related to "terror birds", the 10' phorusrhacids. Interestingly I haven't seen any of the giant, extinct skeletons with a "killing claw" like a seriema (but, not being a phorusrhacid student, they may very well exist).