Yakuza 0

Mr Shakdown appears at various points, he is huge and on the mini map has his own unique icon.

I would recommend avoiding this fight in the first couple of chapters, as losing will mean losing your money instead wait until Chapter 4 as you will unlock Slugger Style with

This slugger style not only inflicts huge damage but blocking with the baseball is able to withstand much more damage.

To Prepare:
Go to the Abilities Tree under the Slugger Branch and increase your health, Power, Wear Equipment which boosts defence and the Security Wallett (this is great as is drastically reduces the cash he steals from you in case you lose) Ensure you visit a convenience store and carry as much of the highest qualiy Toughness health drink and also carry drinks which give you a Heat Boost.

The Fight
The key to the fight is blocking/ his attacks, your bat should withstand most attacks and then pummeling him with three hits, try and use the combo of X,X,X, Y. Also try to evade and get around his
back wh. Don't go blow for blow as he will win. Either block or evade his attack, do your combo and you will whittle aich is a great wy to drop himaway his health. Once your Heat meter is charged get close with your block up then unleash the Special move also remember to drink Tauriner ++ to boost your Heat. Remember that once your health gets low you can use the inventory to drink a health potion.

Provided you have filled your inventory with Health/Heat drink and unlocked a few abilites this should pose much of a problem. If you can defeat him you should be getting around 10mill so its well worth it.

Not too bad of a challenge as long as you're patient and whittle his health down

A couple of little things to note:

I wouldn't recommend doing this until you've upgraded your max health a few times
Make sure you have plenty of healing items
One of the harder parts of this achievement is simply finding him. I personally have no idea of his spawn points so you'll just have to get a bit lucky
There is an upgrade you can buy at the Shrine that will increase his chances of spawning in the park. It's not an ideal place to fight him but it can be done there. It's actually the place where I got this achievement
I also recommend finding the nearest save spot when you get in sight of him just in case you lose the fight so you can reload your save without fear of losing all your money. Another thing worth mentioning is that you cant keep reloading a save if you do find him as he will be somewhere else when you reload the save. So you cant trial and error him by continuously reloading your save and retrying

As for combat I simply ran circles around him and keeping track with the free cam. He has an attack where he'll charge you and another where he will throw punches. They're pretty easy to bait out whilst keeping a good distance away. Go in for a couple of hits and back away and continue circling him. I simply repeated that process with Kiryu using Thug Style. Its not an ideal method and can be quite time consuming but its how I unlocked the achievement. One last thing is that I don't think you can use Heat Actions on him because I don't think he can be grabbed. So don't go in for a grab and leave yourself in a position to get attacked.

Good luck