You know how people write LOL but they didn't really laugh out loud? Well, when I saw the photo of the attenuata, I actually LOL'd. I'd yet to see an agave that sort of looks like a boiled artichoke. I know, I should be murmuring sympathetically, but attenuata is so common where I live (Southern CA) that it's not like it's a one-of-a-kind collectible.

Your 'Quadricolor', well, that IS more of a loss, especially if you paid what I think you paid for it. (Here, even wholesale, they're $30.) Unfortunately, once an agave's leaves are damaged they don't recover, and agaves keep their leaves a long, long time. Wait until the damage turns putty-colored (a week or so) so you can tell exactly what's healthy and what isn't, then trim the damage. Don't cut straight across; for aesthetics, trim each leaf to a point.

With the damage mostly on one side, it may take awhile before the plant regains its original pleasing symmetry, but consider it an amputee that fortunately will regenerate its lost limbs. As with most succulents, new growth is from the center of the rosette, and the bottom leaves become less prominent and may even wither and dry as the plant grows. However, 'Quadricolor' is very slow growing, so if you don't want to look at it, toss it. Which is what you'll probably want to do with that (hee-hee!) attenuata.