I'll just bring this up again since it hasn't been addressed yet. What I believe to be the most underrated mon in the list.
C -> C+/B-/Hell even B : Umbreon is one of the best mixed defenders and is capable of easily taking any non-super effective hit bar Zard Y's Fire Blast. It performs the same cleric role as Sylveon (which is at B) with better bulk, Foul Play instead of Hyper Voice, and inferior typing which could be situationally better depending on the rest of the team. With defensive investment, Umbreon becomes a cleric with the same specially defensive bulk as Sylveon as well as a wall with a defensive bulk just very slightly below that of Mandibuzz (and without the SR weakness) with STAB Foul Play to punish physical attackers. Also has an edge over Sylveon as a status absorber with Synchronize.
I've never been impressed with Umbreon, not at all. First thing is that it has very disappointing abilities that are not beneficial at all (I guess Synchronize is ok, but come on). My main issue with Umbreon is that it is not like Sylveon, it's very one-dimensional and the thing in common with them is that their defensive Eeveelutions. Sylveon completely eclipses it because it has a far superior typing and it is such a huge Taunt bait it's unbelieveable. Foul Play is nice and all, but I would not count it as a warrant to use it over Sylveon. It's ok, but it lacks offensive prowess, is kinda hard to fit on most teams, Sylveon eclipses it, and it is just Taunt / set up bait. I think it's fine where it is, but C Ranking would be the highest it should go. You can't honestly tell me Umbreon is in the same league as Sableye and Shuckle, or even Gothitelle and Sylveon, which are all much more consistent. In C+ even, it doesn't fit with Krookodile and Espeon. I think it should
Stay in C- or move up to C.
EDIT:
Another Pokemon who I believe should move up is Chansey. Chansey is a very versatile Pokemon with many support moves including Wish, Soft-Boiled, Aromatherapy, Stealth Rock, Thunder Wave, Seismic Toss, Toxic, and much more, it supports its team very much and is a key component to Stall teams. It is notoriously known as one of the most bulky Pokemon and for a good reason, it's really freaking hard to take down with Special moves, and even some Physical attackers cannot break through Chansey. Now before someone gives me the argument:
"But Knock Off makes it complete crap!" Well if you're using Chansey, then don't keep it in on anything that could potentially have Knock Off, if you let its Eviolite get Knocked Off then you are not using Chansey correctly and it is a complete waste of a Pokemon. Therefore, I believe Chansey should move up to
A Rank. The key problem with Chansey is that a.) It is Taunt bait + setup fodder and b.) It lacks resistances. Taunt completely shuts Chansey down, and with Gengar rising in popularity with Taunt, Chansey is struggling. Chansey is completely shut down by Steel-types immune to Toxic and a top tier threat, Aegislash, is completely immune to anything Chansey can throw at it. Chansey is also very easy to set up on, however any setup sweeper must beware of Toxic, but if they have Substitute then Chansey is as good as dead. Finally, resistances is a key problem. What holds Chansey back is its Normal-type. Normal-type offers 0 resistances, and therefore it lacks the amazing synergy with some Pokemon like the infamous VenuTran. It does come with only one weakness, Fighting-type, so that's cool. Chansey can take most hits thrown at it anyways, but the lack of resistances is a nail in the coffin. Overall, Chansey is an amazing Pokemon and provides so much for its team that I believe it should move up a rank.