Is the language of all ucv with u ≠ v context-free?
This is a CFL, but the complement (with equality) is not. Notice that both the language and the complement become CFL when you mirror one of the two words.

To show that this is a CFL, you can design a PDA that guesses the letter at position $i$ that will be different in $w_1$ and $w_2$. It start by reading the first $i$ letters of $w_1$ and pushing $i$ symbols to the stack up to this letter, and remembers the letter $a$ in $w_1$ at position $i$. Then, it waits to read $c$, and pops the $i$ symbols off the stack. It accepts if the current letter (at position $i$ in $w_2$) is not $a$.

You have to also treat the case of different lengths, but it's not hard, I leave it as exercise ;)