$L_1$ is clearly a DCFL and DCFL is closed under complement. Hence, $L_2$ is also DCFL.
We can make a PDA for $L_2$ , using the same PDA for {aⁿbⁿ} as follows:
Start by pushing each 'a' on to stack. When b comes start popping. If 'a' comes after a 'b' or 'b' comes when the stack is empty, go to a final state from where the PDA accepts any string. Otherwise, at the end of the string, if stack is non-empty, accept the string and if stack is empty, reject the string.