For his last target, Yahoo, he strongly suggested the company can its CEO, Marissa Mayer.
And now he's got a new target.
Jackson is calling for change at Viacom, the American media conglomerate that owns Nickelodeon, MTV, Paramount Pictures and more.
In this presentation, he argues that the company's complacence is the reason why Viacom's stock is trailing its peers and in the midst of a lost decade.
Sumner Redstone, the company's 92 year-old CEO known for eccentric behavior, has stacked the board with 11 loyalists with no accountability, Jackson argues. The result is that the company has totally missed the digital-media revolution and there is a "creatively bankrupt culture" at the firm.
Check it out below.