No amount of preparation in the universe bridges the gap between a human and a universal-tier Saiyan.
Look, we love Batman. 'With prep time, Batman beats anyone' is a beloved meme. But there are limits, and Goku is so far past those limits that this discussion is almost absurd.
Goku can destroy universes with his fists. He moves millions of times faster than light. His body autonomously dodges attacks faster than thought. Batman is a man in a bat-shaped Kevlar suit who is very, very smart.
Even with unlimited prep time, Batman has no access to technology that operates at the universal scale. He could build the most advanced suit in DC history and it would still be vaporized by a casual ki blast. There is no kryptonite equivalent for Goku โ Saiyans don't have exploitable weaknesses at this level.
Batman's contingency plans work because his opponents have specific weaknesses (kryptonite, fire, fear). Goku's weakness is that he's kind of dumb and lets enemies power up. Batman can't exploit that in a fight.
Batman is the greatest tactical mind in fiction. He has defeated gods with preparation. He... honestly, there's no realistic argument here.
Goku could sneeze and accidentally destroy the planet they're standing on. Ultra Instinct Goku reacts to danger before it exists. This matchup isn't competitive at any level of analysis.
Goku wins so completely that this matchup is essentially a meme. Batman is the greatest non-powered hero in fiction, but there's a difference between 'non-powered hero' and 'universe-busting alien warrior.' The difference is about 10 billion orders of magnitude.
Batman also fights
Goku also fights