Dueling against Bandit Keith can still rely on luck due to the nature of his coin toss tactics.
Use the lower level monsters as protection and to also thin your deck.
Take 1800 damage by either letting him attack you, or use Mirror Wall during the end of his turn, and pay the cost on your turn.
Use the skill Reinforcements to get Plasma and special summon him if Keith has Blowback Dragon, or Barrel Dragon.
If you summon Destiny HERO - Plasma to take control of Blowback Dragon, you will still need to use defensive spell/trap against his Barrel Dragon since he can still get over your Plasma using his spell/trap cards.
Use the lower level monsters and keep destroying keith's monsters. Don't attack if he has a face-down trap since it could be rare-metalmoprh. Set a magnetic mosquito if you think he will tribute summon either blowback or barrel dragon. Use acid raid if you don't have mosquito to destroy his tribute monsters. It's best to summon BEUD during second to last turn to avoid it getting destroyed early. On the last turn, summon vassal and use the union attack combo.
Summon either the hunter or jerry and destroy keith's monsters when they are in defense position to not lower his LP. If they are summoned in attack position, switch it to defense using otohime on the next turn. Acid raid if their attack is higher than yours, or mirror wall to defend as well as reducing your LP. Lower your LP to more than half of keith's LP and keep destroying his monsters so the BEUD can get a direct attack to deal 10,000 damage after equipped with sword of deep-seated.
Keith uses three machine dragons: Twin-Barrel, Blowback, and Barrel. Those monsters have high ATK in current card pool and effects destroying cards you control additionally.
Machine and coin toss supports
He enhances his Machine monsters' stats and effect by using equips cards for Machine-type monsters and Second Coin Toss.
Since the ATK of Twin-Barrel Dragon is 1700 and same to that of Axe Raider, the highest ATK level 4 monster you can get, you need to use equips spells or other ATK boost cards to get your monsters to defeat the dragon.
Use Spell/Trap removals
Destroying Keith's Machine Conversion Factory, Second Coin Toss, and Rare Metalmorph is important to help your monsters to beat Keith's Machine monsters.
This is what i use to farm keith and is inspired by the d-hero plasma farm deck used for alexis. Maybe im just getting lucky but it feels pretty consistant.
Using a Hazy Flame deck with Mai can also produce some good results, but you have to get lucky and hope one of his twin barrel dragons don't blow up your beast rising. Other than that; that's another strategy.
This Deck I'm using is getting me a 90% of winning rate against Bandit Keith... I just hate that i have gotten a lot of cards from him, like 10 copies of each rare and some SR, but just 1 Rare Metalmorphe... e.e
don't bullshit, when the opening hand is not good then he finishes you!!! won only 3 times out of 7 with your deck.
Leukocyte
Heya! I've made a pretty consistent 7.3k Labyrinth Builder deck for this guy. Hope it helps you all farm him.
Decklist:
x1 Anteatereatingant
x1 Gravekeeper's Vassal
x2 Cat of Ill Omen
x3 Cosmic Compass
x2 Union Attack
x3 Stray Lambs
x1 Shield and Sword
x1 Secret Pass to the Treasures
x3 Good Goblin Housekeeping
x3 Tyrant's Tirade
x1 Blue-Eyes Ultimate Dragon
How to use: Stall turns with Stray Lambs/Cat/Compass untill you have x2 cards in hand for Labyrinth, x1 Tyrant's Tirade, and either x1 Stray Lambs or x1 Cosmic Compass. Get your tribute fodder out with your Wall, activate your trap, pass turns and draw cards with Good Goblin Housekeeping, last turn activate Shield and Sword, set 1 extra card and special summon Anteatereatingant, change Wall to attack mode, summon Vassal, secret pass, union, union attack for 10k.