Shadowverse

all sorts of Pikabu and similar places

Well, this is a YouTube video from the early 2010s.

It didn't drop for me. Although before, title Legendaries used to drop regularly.

So, it will drop soon.

It's a pity that it's just a meme. I heard that it's used in the Portal, either instead of the Machine Goddess, or together with her, or they just create a Mill Portal and then hide behind Wards from Aegis.

I saw a couple of them, somewhere at the beginning of the expansion. It's probably fun to burn cards with heavy decks, but more aggressive decks will only be grateful for Cronos (although they will probably kill you before he comes out).
There was also a P/D/K deck with him, but after the nerfs, they disappeared somewhere.

One streamer played on the Portal and on the Dragon with Cronos, after which I personally encountered both in ranked. In the Portal, he hid behind Nilpotent Entity while the opponent died of fatigue, well, in general, the deck is complete garbage, but in the Dragon, it's sort of viable. Against your spammed board, he puts down P/D/K with minions and clears the board + deals some damage to your face, or throws down a Dragoon, destroying both the board and your face, and immediately draws new cards. When I played on the Dragon, it was absolutely impossible to win against this deck; you can't throw out Bahamut, or Sahazris, or wait for him to fatigue himself, in short, you can't win. I'm not sure if you can consistently play and climb with this, but the deck is very dirty, and it shouldn't exist.