The absolute worst are GAMO. Not just the scope the whole gun. As far as accurate the Daisy target rifles are very and I have a QB78 by Industry that is very accurate and easy to shoot, it uses 2 CO2 cartridges. All in the 100-150 range. These guns are not real powerful. And they have almost no recoil and do well with cheap scopes or target sights. For spring/air guns you need a scope rated for them, I have had good luck with Winchester air rifle scopes. You need a recoil stop on the bases. You might want to check with an air rifle specialty site like Pyramid. I like to buy air rifles from Mike at. Flying Dragon Air guns. He stocks better quality Chinese guns and others. He tests each gun and will do custom tunes and is cheap. Yeah it is frustrating. I use them for plinking and small pests. You pretty much have to go $$ PCP for high power or long range. I don't like the way you have to shoot spring guns.
One of the few things that gets my hackles up are statements like X are the worst. I had a chevy that puked its transmission at under 20k miles....does that mean that General Motors makes the worst cars....no.
Problem with Gamo is where they are sold.....Walmart, and who they are sold to. People with very little experience shooting high powered spring air rifles. A high powered or "magnum" air rifle is THE HARDEST THING TO SHOOT. Thats it....nothing is more difficult to shoot well time after time then a magnum springer.
Now you stick these very hard to shoot guns at walmart for a price that is just amazing for what they do and naturally you get inexperienced people that say they are garbage. Toss in there that SOME pellet guns can be very pellet specific...love some hate others....it is going to be a bad outcome.
I do not want to single out the OP. Or the guy I quoted here. I have a case full of air guns, some that I had given to me that would not shoot for anything....could not keep pellets on paper at 25.....After learning the gun and its specifics every tomato stake I was given is a great shooter.
I wanted to include a pic of one of the cabinets that I have....everything in here is an air gun....everything from a sub $60 Walmart hunk of junk to a 50+ year old anschutz....and everything in the middle.
In this day and age of computer controlled manufacturing are really bad guns going to get out there....sure it happens but not very often. And another thing to remember is that most Gamo's are still made in Spain, not China....That really means zip to me, but it seems to matter to some people.
In the end like I said there is a great learning curve to shooting a high powered springer well....does not matter whos name is on the side of it.
Now on the the photo....not everything I have is in this photo, some stuff is in other gun cases and safes.