I am just going to add Fortran (programming language) to the mix. I am happy that it is has not been mentioned because that means others have not had to suffer. Arbitrary array indexing, (in older versions) arbitrary formatting rules involving column placement, case insensitivity, cryptic 8 character variable names, implicit types based on the first character of a variable name.

Often you have to work on legacy systems where the code has been around since 1977 and the developers wrote code without any thought of maintenance or craftsmanship. It is just hard to read, hard to maintain, and unfortunately still prevalent in my community.