@RaichiousMuffin
Wow, I really like your art of Dan and Keanu. You don't mind me sharing it on my Instagram and giving you a shout-out? Keanu sounds similar to Bolten, He was a martial artist and also used lightning-based attacks. I still have the link to his fight with Dan in my original post.
Dan himself is quite mobile on his feet stepping in and out of range of attacks. He also exhibits head movement as shown in his fight with Bolten and later end of his fight with Behemoth Man. Even when taken by surprise he was able to slip bolten's attack at long range. Dan is also keen on making adjustments throughout the fight by recognizing patterns and scoping out openings. So it won't be easy for Keanu to land the jab unless he has a huge speed advantage and is quick enough to react to Dan's blitzes. Even so, Keanu would have to exhibit Behemoth Man's level of power and durability to kill Dan or slow him down. Although you admitted Dan is physically stronger than Keanu. You'd have to send me links to Keanu's fights to better assess him.
Similar to Garou from One Punch Man, Dan will continue to get faster and stronger as the fight continues. If you don't kill him he will become more of an issue as the fight prolongs.
The deciding factor of this fight will come down to Keanu's durability and the potency of his bullet-fist technique and lightning ability. Dan was able to fight through broken bones and crushed internal organs with his heart being pierced. That was after being punched through several walls and falling down several stories of a collapsing building. Could Keanu fight through such damage? If so its gonna be a really hard fight for Dan.