Promised Consort Radahn ruined the whole DLC

I’ve been enjoying the Elden Ring Shadow of the Erdtree so far until I got to the end. I'm not an Elden Ring expert but obviously good enough to get to the end of the DLC. This DLC final boss is bullshit. He attacks non-stop and leaves like one opening that you have to be perfect otherwise you miss it. That means, you cannot even heal yourself because he will come and get you. I've only tried maybe 20 times so far so I'm not giving up yet. I've been watching those hitless videos to see if I can do the same but so far, I feel like this final boss ruined the DLC otherwise, it would’ve been perfect. Malenia was impossible but was fair IMO. this one is utter crap...