The worst F2L case

(R U' R') (r U' r' U2 r U r') R U (F R U R' U' F') R' (r U' r' U2 r U r') (R U R') R (F U R U' R' F') U' R' (R' U R) (r' U r U2' r' U' r) R' (R' F' U' F U R) U' R (r' U r U2' r' U' r) (R' U' R) R' U (R' U' F' U F R) R Even just considering the basic 41 cases, there are a few that could reasonably be considered the "worst F2L case" (most notably these, or a single flipped edge). I chose to focus on these ones though because the solutions I generally see people using are kinda awful (stuff like R U' R' y' U R' U' R U' R' U' R). However, if we're willing to delve into "algorithmic" F2L a little, it turns out there are some pretty nice solutions - and what's more, it's very easy to solve ZBLS, because there are only two possible cases we can get. Note: there a variety of ways to solve these, I just showed the solutions that I prefer. Stuff like r U' r' U2 r U M U R' or F' r' F2 r F R U R' can be very fast too though, so it's worth experimenting to see what works best for you.