My brother and I were discussing the different types of clone character, and we've devised this essential "clone tier list" for defining the distinct strata of clones. Note that this is very much a subjective perspective and just something we did for fun. If you have any issues with it, please feel free to mention them, just remember that this is not intended to be an authentic quantification of a character's inherent "cloneness". In descending order, from least clone-like to most clone-like, we have:
F TIER - NOT EVEN A CLONE
Very vague similarities in certain areas (character model, a small number of standard attacks), but otherwise totally distinct. Not even remotely a clone, though sometimes jokingly or fallaciously compared to one.
E TIER - LUIGIFIED CLONE
A character that was originally a clone of an existed character, but whom has since evolved into their own character. They may possess certain similarities in terms of moveset elements (for example, Luigi's neutral-b and up-b are variations of Mario's), but their overall playstyle and stats are so vastly different as to render the term "clone" largely redundant. In short: once a clone, and a clone no longer.
D TIER - SEMI-CLONE
A character with a few noticeable similarities to their original counterpart, yet whose differences are distinct enough to separate them and render them mostly unique. Most often, their specials are similar in concept to the original character's, yet they have different applications and almost all of their standard moves are unique or at least function differently. Their stats are also usually quite different.
C TIER - NOT QUITE FULL CLONE
A character whose overall moveset is very similar to the original character's, yet whose unique moves are enough to set them apart. Their specials are, for the most part, almost identical, and they have many standard moves of a similar nature as well; what moves they have of their own, while few, are nevertheless distinct enough to stand out of their own accord. Their stats are also usually very different, offering a totally unique playstyle.
B TIER - ALMOST FULL CLONE
A character whose moveset is almost identical to the original character's, with only a few key differences setting them apart. Essentially, they're somewhere in between C tier and A tier: not quite identical, yet not that different. Usually it's only a few subtle moveset differences and / or stat alterations that set them apart.
A TIER - FULL CLONE
A character whose abilities are only very subtly distinct from the original character's. Their moveset and stats are, overall, unaffected, with only very minor differences setting them apart.