How to put two images next to each other in one table row?

You nearly got it, the images need to be individually wrapped in a box.

#set table(
  stroke: none,
)

#table(
  columns: (auto, 1fr),
  inset: 10pt,
  align: (center, right),
  [Front Punch],
  image("square-512-Flat-Playstation.svg", width: 4%),
  [Back Punch],
  image("triangle-512-Flat-Playstation.svg", width: 4%),
  [Front Kick],
  image("cross-512-Flat-Playstation.svg", width: 4%),
  [Back Kick],
  image("circle-512-Flat-Playstation.svg", width: 4%),
  [Uppercut],
  box(image("d-pad-down.png", width: 4%)) + " + " + box(image("triangle-512-Flat-Playstation.svg", width: 4%)),
  [Blade Slash],
  box(image("d-pad-left.png", width: 4%)) + " + " + box(image("square-512-Flat-Playstation.svg", width: 4%)),
)

No need for to explicitly start code mode with # as you already started it with #table(...). You would only need it if you switched into content mode (square brackets) again e.g. you could also write:

...
[Uppercut],
[#box(image("d-pad-down.png", width: 4%)) + #box(image("triangle-512-Flat-Playstation.svg", width: 4%))],
...

Thanks for using code blocks :)