When did the trend of powerful slimes come about in Anime? Slimes are commonly known as the weakest creatures, but more and more I'm seeing powerful slimes show up in anime. When did powerful slimes become a thing? Or have they always been a thing and I just haven't seen them around before?
Earliest example I can think of:

Overlord - Solution Epsilon. Anime 2015, novels started in 2010.
Konosuba - Season two finale, Hans. Anime started 2016, Novels
in 2013.
Reincarnated as a Slime - Anime 2018, Novels in 2013.

I'm sure there's plenty others as well.
The trend began when the anime called, “That Time I Got Reincarnated as a Slime” started serialization. This show started in 2018. I don’t know if someone already had an anime that was about powerful slimes before the anime “That Time I Got Reincarnated as a Slime”, but I am sure that they were not as popular as this anime. There are a bunch of anime’s that are about slimes that started after the anime “That Time I Got Reincarnated as a Slime”.
If you want more info, here’s a website that I got all of this info from: https://www.cbr.com/slimes-taking-over-manga-anime/.
I hope this helped