Bear case

The scenario in which the thesis fails, and the one that decides position size.

The useful version is specific about mechanism rather than degree. Not revenue growing 6% instead of 12%, but the largest customer insourcing, the patent expiring, the regulator changing the tariff, the funding market closing.

Writing it first, before the bull case, is the single most effective correction for confirmation bias in investment work.

The downside is the part you have to survive.