What the achievement asks for
A developer reply in the official Steam discussion states that Defy the Odds is earned by beating the game with the Pity system turned off. Beating the game here means completing the collection run, not opening a set number of packs. Finishing with the protection active does not count, even if the rest of the collection is identical.
The in-game name for the Pity system is Bad Luck Protection. Players in the same thread found it under General Options in the settings menu. Turning it off is the only extra condition the developer has described for this achievement.
Why most players miss it on the first run
The developer explained that the Pity system is on by default because most players are casual. Bad Luck Protection smooths out long droughts of missing cards, which makes a normal run more relaxed. Because no prompt appeared at the start of a save in the version players discussed, many only learned about the option after the credits.
Several players asked for the choice to appear when a new game begins. The developer response encouraged replaying the game for the achievement instead of offering a retroactive unlock. Treat a first run with the default settings as a normal completion, not as progress toward Defy the Odds.
How to plan a run without Bad Luck Protection
Open General Options before you rip your first pack and switch Bad Luck Protection off. Check the setting again after loading the save, because one player reported that settings appeared to reset when starting a new file. A quick look at the menu early costs nothing and avoids discovering the problem at the end.
Without the protection, the last missing cards can take noticeably longer to appear. Selling duplicates for cash and investing Gadget Points in the Rip Rig and Binder Bot keeps that grind manageable. The automation guide on this wiki covers how those tools speed up a long collection run.
If the achievement does not unlock
One player in the community thread reported finishing a run without the achievement appearing. The developer has not published a fix or a confirmed cause in the material reviewed for this guide. If it happens to you, report the details in the official Steam discussions, including whether the setting stayed off for the whole save.
Before blaming a bug, confirm that the option was disabled from the start rather than partway through. The developer wording describes beating the game with the system off, and it does not say whether a mid-run change counts. Starting a fresh save with the option disabled is the safest reading of that rule.