Biggie and Tupac ruled the 90's. They swore a ton. It's possible to find a decently long playlist of songs without (much) swearing (I wouldn't call O.P.P. clean) from the era (I actually have one), but a lot of those songs were exceptions for the artists or at least didn't represent their entire work. Wyclef and Lauryn Hill, for example swore a decent amount on some tracks and not at all on others.