Creed II brought back one of Rocky Balboa's toughest adversaries, but the two never actually get physical in the movie. However, it seems originally they were going to do just that. Sylvester Stallone himself recently released some behind the scenes footage of the filming of Creed II which shows himself and Dolph Lundgren going through fight choreography for a scene that ended up on the cutting room floor, which would have had Rocky and Drago trading blows for the first time since Rocky IV. Check it out.
According to Sylvester Stallone's Instagram post, this scene would have taken place after the first fight between Michael B. Jordan's Adonis Creed and Florian Munteanu's Viktor Drago. In Creed II we see Rocky visit Adonis in the hospital, where he's basically thrown out by a frustrated Adonis. It seems that originally there was a scene where Rocky, as he left the hospital would meet up with the Dragos and the fight promoter who have brought a camera crew with them to harass Creed. Rocky stops them from going to Adonis' room, but it results in Rocky and Ivan getting into a fist fight.
Based on the choreography we see here, things don't go too well for Rocky the second time around. It looks like Ivan pretty much wipes the floor with him until the hospital's security steps in to break things up.
On the one hand, it would have been pretty great to see Rocky and Drago mix it up one more time. While both actors have gotten older, they clearly both still have the energy to put on a scene like this.
At the same time, giving Rocky his own action sequence, would, in some ways, defeat the purpose of Creed II. The film was very much designed to be the launch point of a new franchise that focuses on Adonis Creed. Rocky doesn't need to steal the spotlight with his own fight scene.
That's likely at least part of the reason why the scene was cut from the final film. It isn't strictly necessary to tell the Adonis Creed story and ends up being distracting from that.
The first Creed movie did a fantastic job of blending the nostalgia for the Rocky Balboa story with a new journey for a new character. Creed II does that as well, the direct connection between it and Rocky IV is obviously that, but it's also about defeating those demons and moving forward anew.
Sylvester Stallone himself has said that Creed II will likely be the last time we see Rocky Balboa on screen. We didn't need to see him fight one more time. We have all the old movies for that.