Comment by tguvot
I have my own sample set as I presented.
Russian is seriously messed up language. Especially after learning Hebrew (which is simple and algorithmic) , I was able to look back in Russian and realize what a horrible mess of a language it is.
Hebrew was literally synthesised a century ago. Language designers really did great work on taking a core of a dead language and proposing a cleaner, more modern version of it.
Russian and English never had this "rearchitecture-and-cleanup" moment. In fact, English borrows heavily from different languages (old german, old danish, latin, old french...) adding even more complexity. Russian borrows from greek, old slavonic (bolgarian), among others. So an advanced speaker/reader of these languages has to understand the influences.
A couple of years ago I tried learning some minimal Ancient egyptian. A fascinating language in its diversity. Middle kingdom egyptian, old and new kingdom written dialects. Then, there's a simplified cursive script which almost feels like modern writing.