It's a little hard to tell from your examples, but I think you are saying that there's a consistent difference in sharpness (and possibly chromatic aberration) on one side of the frame compared to the other.
If that's the case, this is unlikely to be a damaged coating. This is usually a de-centered or slightly tilted lens element.
Nothing is perfect, and all photographic lenses have compromises in order to reach their design goals. This particular lens has sixteen glass elements in fourteen groups. These elements enable the huge zoom range and other features like internal focus, image stabilization, and reasonably close (although not macro) focus. All of that in a package that sells for $200 retail brand new.
Even the most expensive lenses aren't absolutely perfect. (See this Lens Rentals blog post on copy-to-copy variation in geeky detail.) They're made to be as close as possible to perfect within quality control tolerances. More expensive lenses can have more fine tolerances (and often are built with more ability for technicians to adjust). Lower cost lenses — and especially complicated lower-cost lenses like your super-zoom — by economic necessity have wider tolerances for acceptable flaws.
So, it's not terribly surprising to see something misaligned. It's really hard to tell how bad this is from your samples, but you shouldn't expect miracles from this lens. It's possible that had you bought this new, you could send it in for adjustment under warranty, but very likely that they'd send it right back with a note that says "tested: within tolerances". This is camera-warranty speak for: Dude, it's a $200 lens. Our profit margin on this was already, like, two dollars. Please don't waste our time.
More on tilted and decentered lens elements at: Left part of image is much softer than the right part: decentered lens or bad M42-EOS adaptation?
Some people deal with this by buying dozens of copies of cheap lenses and returning them until they get one they feel meets their personal standards. This is not very fair to your camera store, however — the economic bargain the vendor is making with you (high-featured super-zoom for peanuts) has the camera store stuck in the middle.
My main advice is to not pixel-peep. This lens isn't meant to create wall-sized gallery prints. It's meant for taking pictures for Facebook and Instagram, for family vacation postcards and maybe some 8×10" prints. And, I think even with flaws (remember, everything in this world is flawed!) you can use it to take perfectly lovely photographs.
If, on the other hand, that's not what you want, I suggest instead spending about 10-20× as much as you did on this lens on two or three nice prime lenses — this is the most economical way to get high quality lenses which require less design compromise and can be closer to the optical ideal.
Or, if you don't have 10-20× the cash just burning a whole in your pocket, you can, like me looking at the Leica S system, think "well, that'd be lovely, but I have to work with what I have, and I'm not perfect at that, so I'll figure out how to make do". Oh, and also: you mention "second glass", which makes me think maybe you have a filter over the front element. This very well may be part of the problem — see Is a UV Filter required/recommended for lens protection? on that.
Also, What image-quality characteristics make a lens good or bad? may be helpful in thinking about all of this.
