I've found a build that allows you to get infinite damage, and I haven't seen it anywhere else on the guides forum, so I'll be writing my own.

This build can be done with 2 upgrades, but is best with a few more. Those upgrades are reckless rush and soothing escape. Reckless rush makes you take 1 damage each time you dash, but gives you 5 base damage. Soothing escape heals you for 1 each time you dash, but increases your base dash cooldown by 30 seconds. This combination allows you to gain 5 base damage each time you dash. On their own these two upgrades take a while to get a good amount of base damage, but adding a third upgrade, steam boots, allows the build to really get rolling. That makes you use up all your dashes at once, but reloads them all at once too. This can let you reload more dashes to use way faster, as you can easily get 10+ dashes. With this build, you should prioritize dash amounts and cooldown speeds. After image halves your dash cooldown time when moving, so that lets you get damage 2x faster. (An important thing to note here is that it doesn't make your cooldown go by faster when you're moving, it halves the requirement while you're moving, so you can stay still until it reaches halfway and then move and it will finish immediately.) Ninja headband also reduces the cooldown of your dashes by 30%.

While the infinite damage build is very good at one shotting enemies, it takes time to reach enough base damage to deal with anything, and time isn't always on your side. I suggest grabbing the following upgrades if you see them, which synergize well:

Uncanny Dodge: Gives you a 30% chance to dodge any damage, including the damage from your dashes, so about 1 heal per 3 dashes.

Emergency Kit: When you take 2 damage in a row, you heal for 3 health. This has a 60 second cooldown, but it will heal you for 3 when you dash.

Active Recovery: Heals you for 1 each time you dash 12 times. It's alright if you haven't got Emergency Kit or Uncanny Dodge yet.

Bloodlust Idol: Hearts won't heal you, but they will give you +3 base damage. Good if you already have any of the three above, as they will be sufficient to heal you.

Gluttony: 10% extra damage per health. Simple, good for damage.

Jackhammer Charges: 5% extra damage per pierce. Again, simple and good for damage.

Bullet Spear: Gives you an extra dash for each pierce you have, helps out a lot, especially once you get a bunch of pierces.

Bloody Rage: Gives 3x attack speed for 5 seconds after taking damage. The time can stack on itself. Read as: 3x attack speed for free.

Surprise Attack: Gives 100% crit chance for 2.5 seconds after you dash. Like Bloody Rage, the time can stack on itself. Read as: Guarunteed crits.

Inner Strength: +5% crit chance for each dash that is ready. A decent replacement for Surprise Attack.

Sheriffken: Gives +5 pierces. Good if you have jackhammer charges (+25% damage) or Bullet Spear (+5 dashes.)

Last Pull: Brings all of the collectibles on the screen to you when you take damage (so when you dash). Good for making sure you don't miss coins.

Onion: Does 30% of your damage to all enemies within your AOE every 0.5 seconds. Your damage should pretty quickly get high enough to oneshot them and if not, the cooldown is affected by your cooldown reductions, so you can spam it very hard.

Mezcal Perfume: When you move 25 meters you throw an AOE poison bomb that spreads from anyone who dies to it. If you have high AOE it should chain on itself and infect everyone on the screen. This can usually keep all enemies off screen until you get unlucky and it kills everything before new ones can spawn to infect.

Godly Die: Lets you upgrade level-up upgrades using rerolls. If you get this, watch for purple cooldown upgrades and upgrade them to mythics (red). The more you can spam your dash, the better.

Literally anything that does damage when you dash, and also Nitro Suit