I'd just grab em with some pliers. Maybe needlenose depending on how small and how the space is.

Those look like brads to me. They may have been glued brads. I use channel lock pliers to pull them out. The curved jaw gives good leverage.

I think you said pliers weren’t doing the job. Grab them with vice grips (locking pliers) and use the claw side of a hammer to pull them off like a nail.

Pair of linesman pliers or needle nose vise grips a block of something to create leverage and use that lever.

Angle grinder will take care of those in seconds!

I always use end nippers. They look like something a horse farrier would use to trim hooves. They have a round face so you can grab at the base of the nail and rock it back with ease. Nothing I have found beats them for speed and ease of use when you're pulling nails/staples through the back of wood.

If you want to do minimal damage, try backing them out the front side with vice grips like another commenter suggested.

Needle nose pliers

Probably too late but at this point I would suggest just worrying them back and forth or just snip them and then hammer or file em flat. Those look like 18g narrow crown staples to me and any version of pulling them means you have a much higher chance of damaging the board a little.

Needle nose pliers or dykes

Straighten them out. Cut them leaving no less than 1/4". Then hammer them through the other side. Then use your channel locks to pull them out.

I've saved hundreds of sheets of plywood doing this.

Use this type of hammer and pull with claw side.

If pliers didn't do the job, I would cut them at the base and sand them down to be smooth and flush with the wood.

Knock them backwards/through or grind them off.

Sometimes the wood closes over them after the last sanding when assembled.

If you don't care about metal in the wood, the you could use a pair of diagonal cutters to snip them flush with the wood rather than try to extract them.

Aren't they nails? If you don't mind leaving them in the wood you can just break down their outside part.

A Dremel would cut those out nicely.