In 1995 we boycotted Shell for environmental reasons and it worked: https://en.wikipedia.org/wiki/Brent_Spar

Towing of the platform to its final position began on 11 June. By this time, the call for a boycott of Shell products was being heeded across much of continental northern Europe, damaging Shell's profitability as well as brand image. [...]

On 20 June, Shell had decided that their position was no longer tenable, and withdrew their plan to sink the Brent Spar [...]

So it needed more than a week of concerted boycott action to bring big business into trouble, but not unlimited boycott.