Underrated: dread gohul, this guy is really good, just start with a stunbomb and hava a sleep bomb after, with that you can pull its death sentence and charge bloodthirty.
Overrated: atrahasis? IDK
Most over rated legendaries
Most under rated the ingame monsters
Underrated: Low star monsters such as Felimancer, Pengboss,and Pterasoar.
Overrated: Aegis.
Well at least they are rated.
Lol aegis can’t be highly rated enough. But agreed with Lochi. Tomb guard is a 1 cost give turn I use very often.
I know I talk about these guys a lot, but sentiguard and the duplicate stunners are seriously underrated. They can set off 2 stuns minimum, and even do a last stand of a sort.
Just gonna do legends here…
Atra is the most versatile and underrated for PVE. He fits in so many different strategies.
Another underrated min I feel is Sanctillion, yeah you need some holy monster to get his Assisted strikes up, but he is the lowest rated legend which is crazy to me. Risky heal, create dupe, and stun revenge. He has saved me in PVP and PVE more than I can count. Not the best mon by any means, but better than he gets credit for.
Overrated, Ziberus, just not that great of a PVE mon in late chapters and events in my opinion. He is good in situations but overall I don’t enjoy him or often find him a game changer.
I agree with both the points about atra and ziberus. I dot think sanctillion is very good though. Ziberius seems great but double retribution just doesn’t do enough damage to be really worthwhile.
Stegospike is great as a stun absorber, it has really helped me through tough spots. So has Dracomander (4 cost for knock back), Storm fox 2-4 cost ( stun bomb), Musharoo/Moji 1 cost ( for sacrifice healing), Grizzrex 2 cost ( for stun revenge, although hold ground makes him weak against poison), Breezehawk (1 cost poison revenge)
Overrated: Probably God feather 
Shout out to Remus in this, not really underrated but only because barely anyone knows about him.
Also aegis is in no way overestimated, trust me. It’s arguably the best monster in pvp right now.
But anyway.
Most overrated I would say is aurodragon. I remember we all went crazy when he was released but it’s so hard to use him properly. Thing is you only understand this when you use him, so people still think he’s amazing. He would be if reincarnation was higher than 30% chance.
Most underrated I would say is probably dolphlare. He’s still suffering a little from his old reputation so you don’t see him that often, but he’s a really solid choice now
Underrated: Helldactyl. That monster has been one of my most trusted Protector/Purify monsters. It’s been on my team since the beginning.
Overrated: Honestly, I’ll say Puffoxin/Rhynobrawl. I understand why people like them, I’m just sick of seeing them everywhere.
I gotta say, godfeather is in no way over rated, he gets the love that he deserves since anyone and every can setup his last bite (mainly in pve) and with zephyrox his assisted thunder becomes awesome in pvp
I think people forget a lot about taloknight and apolorexus but they’re really powerful when use by a competent player like shomy. As for the overrated I would say aurodragon, he’s just bad.
That’s exactly the reason why I think he’s overrated. Anyone can easily use him and it doesn’t really take much strategy to implement him into any team. He’s by no means a bad monster since his last bite pretty much wins entire battles. I just think its a monster that people just go to as one of those metas to quickly end events/challenges/story related PvE without overthinking anything. From what I’ve been figuring out he’s not really all that useful in the ultimate challenge at the higher levels.
Personally, I never really found him all that appealing. Putting aside utility, he was my first legendary and before I came here I never knew he was that good. I never really used him at all (until recently when I ultra-evolved him), because he just didn’t seem that interesting to me. Yeah, I get people like him because he’s so good but I just don’t really like the design that much. I was legitimately disappointed when I first got him because it wasn’t one of the legendaries I wanted.
From what I’ve observed in this community since I got here, he definitely already gets enough attention (from the several mods that have him as an icon to the users in the other sections who’ve I’ve seen ask for people’s accounts if they have that monster. People restarting and going specifically for that legendary as their first egg and youtube videos of people hatching a penguini and people going nuts about it)
I wouldn’t take something away from any mon on the fact they’re not that useful at higher levels in ultimate challenge.
Barely a handful are.
fair points, I only use his last bite in emergencies / pve events since they can be a bit of a drag and I really have nothing else 
but I can see where you’re coming from, everyone wants him / uses him and he’s fairly op
I want apollo that bird is baddass
Yeah, you have a point.
I think I might of used the wrong word for Aegis. It’s definitely not a bad monster. I think I read it wrong and used the definition of over-hyped instead of overrated. All monsters have their place in this game. Aegis I believe is an awesome monster, however I do feel that because of its popularity it overshadows other monsters. I don’t PvP much so I don’t use that for monster ratings much. But when I do it usually see the same set ups around certain monsters, which limits creativity and makes metas stagnant. I do understand that players will choose what’s the most efficient setup. However, that’s another topic to discuss.
So, If I had to pick again I’m not sure I could since all monsters have a use in this game. Even if they’re not good for one event I’m sure they’re good for another. 