#4. Illegal tactics
Illegal tactics to win isn't really a babyface thing (with the sole exception of Eddie Guerrero), it's not something that we haven't seen before. Finn Balor, from a physical perspective, would obviously stand no chance against Brock Lesnar. The entire match will feature him getting rag dolled.
This is why in order to win, Balor may use a weapon, or worse, might go down low the way Daniel Bryan did to win the WWE Championship. It wouldn't necessarily turn Balor heel, but it could add an edge to his character and make him a tweener, something that's far better than being a smiling babyface.
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#3. Avoiding high-flying moves while Lesnar is up
In kayfabe, trying to fly high while Lesnar is in the air is the worst possible thing to do. We've seen it with superstars like AJ Styles before, where they try to fly high, only to be caught mid-air and hit with an F-5.
Balor has the agility and is a high-flyer, which would mean that he knows exactly what to avoid to prevent getting pinned.