Yeah the final stage and especially its boss can be very difficult if you aren't prepared. For the longest time I thought a clear wouldn't be feasible simply because of how punishing bad ABSNet timings/recharges can be in that last level.
I had to save-state practice it and study the final boss too in order to stand a chance, and that training really paid off. Even then, in the run I came into the final stage with full lives and cleared with only my last one left
