Years ago (20 years?) down by the lake I did a stacked running bond wall out of bags of quikrete. Approved by the town. I cut maybe a 10" x 12" square of paper out of the side of each bag as I set them, so mix would be touching mix from course to course. Maybe 24" tall total. Very slight offset between courses so the wall leans back into grade. I planted ivy on top, the ivy cascades over to cover the facade facing the water. There has been minimal degradation over the years with New England freeze/thaw cycles.
Quikrete for one has an official bagged product for this, called "Rip Rap". Wasn't available in my area back then. It's laborious, but it does go fast.
Right now I'm doing a wet wall, with a bit of an "S" curve to it. Roughly 38" high. Stones are from digging on my property, the cement mix is screened subsoil mixed with portland. Done on the cheap. The facade of stone is dry stacked, then everything behind is infilled with mortar and additional stone from behind. I'm not much of a mason, so this was my best solution. Overall it keeps the stone on the face of the wall looking fairly clean. I use cardboard boxes and pieces of scrap ply and even a couple of old pallets on the back of the wall as I build vertical, it prevents the wet mix from oozing out. Not the proper way, but it's my way. lol Then the next day, shift it all down to the next part of the wall. Two weeks and I've done maybe 60' complete with another 15' partially done. Another 40' to go.
More labor required than the retaining wall made from stacked bags of cement, takes longer, but looks better.
Fastest would be those modular concrete blocks. A few weeks ago I was getting a slew of FB marketplace adds for "Australian Limestone Blocks" (I think that's what they were called). Same idea, I'm guessing it's a slightly prettier version of those large concrete modular blocks.
This would be fast, and with hydraulics doing the heavy lifting it would be easy on your back. Though you'd need equipment with access to stack the wall. And those "limestone" blocks looked decent, at least in their ads.