All languages: Let's make sure our words for counting are short.
All languages: Yeah, that's a great idea!
Finnish: *knocked out by too much Koskenkorva*

Swedish 'u' and Japanese 'u' a very very close.
Which is why I'm sad that all Swedes think all foreign languages use German 'u'._.

Tom Scott made a short video about it:
https://youtu.be/s6kNR8Mj0ZE

So if we go back to the girl in the post, people who base their view in IRL or fanservice-free anime would certainly call her "huge" or maybe even "exploading", but for us oppai connoisseurs would probably classify her as 並乳 "normal-sized" or 美乳 "beautiful-sized".
So for some, Thunder Nyan Nyan is absolutely oppai loli, but for some absolutely not.
As for me, I didn't think I would be part of the community here when I registered just to browse some memes, so I just picked something I liked. In hindsight, probably not my brightest moment. But as no one has called me any hurtful names yet, I guess I'll keep it for the time being. (｀･ω･´)

When it comes to oppai, the situation is rather messy as well. First of all, what we outside call oppai loli, isn't called oppai loli in Japanese. The most common expression is ロリ巨乳 'rori kyonyuu' "loli huge b00bs".
Japanese is a language with less specificity than western languages, e.g. 足 'ashi' means both "leg" and "foot". In the same sense 巨乳 "huge" refers to both all kinds of big sizes, but also the smallest of the big sizes.
There common three-step scale is 巨乳 "huge" <　爆乳 "exploading"　< 超乳 "super". The latest category is almost exclusively used for >ridiculously< big sizes even for anime-standards. However if you compare what is considered "exploading" IRL it can be relatively smaller than the lower end of "huge" of 2D.
There was a tweet floating around Japanese twitter recently how people who liked small would classify what is "huge" and "exploading", versus how people who like huge classify "huge" and "exploading": it's all relative to what you're used to.

Loli is really a question about definition and it wildly differs between both Japan/rest of the world AND whether it is referring to real people or anime girls!
When it comes to 2D, it usually refers to prepubescent/elementary girls. But as xvarnah pointed out, it isn't the age as much as the looks. Loli Babaa (loli granny) is what those sometimes hundreads or thousands year old >women< (mind is adult) that look like they're 12 are called.
On the other hand, if you look for "loli" pr0n it refers to adult women with very young looking >faces<. The word for CP doesn't contain loli, but 児童 'jidou' for "child" so loli-ism and CP are treated as entirely different things. (Actual CP is very much illegal in Japan)
In Japanese, the origin word of "lolita" only refers to the fashion style.

Honoured to be welcomed back in such a fashion!
As lydia pointed out it is indeed Echidna from ReZero.
The reason why you didn't find it in reverse image search is that I commissioned this artwork for the specific purpuse of having a unique pfp online. So if you see this somewhere online, it's probably me. (Unless someone downloaded the cropped pfp from one of accounts; only I and the artist have access to the full-size and uncropped picture.)
The question about the most oppai loli card in YuGiOh is a good one!
Hadn't really thought about it, and you're quite correct there are quite the number of both oppai and loli, but not really any oppai lolis!
After discussing it with a friend who occasionally still plays YuGiOh, our best guess is perhaps LiveTwin Ki-Sikil?
But Thunder Nyan Nyan isn't a bad candidate either.

Was gonna say the same

My guess it is the name of an exchange student who drew this: Olivarescoco or something like that

CDB is correct. Furthermore, above it it says 特技 "tokugi" which means something special you can do or your party trick.
I guess up left is the name of the program, 日向坂で会いましょう let's meet on the sunlit alope.
Up right is probably the segment of the program cause it again mentions 特技, but the picture is to grainy for me to make out everything so I'll just leave at that.

Don't know where the line goes, but somewhere it stops being
[personal integrity] > [history] and flips to [personal integrity] < [history].

OH OH N- *static*

WE'VE LOST VISUAL ON PADORU!

PADORU HAS REACHED MACH ONE, I REPEAT, MACH ONE!