Pharmaceuticals giant Pfizer got a wake up call Sunday evening when one of Wall Street's most feared activist investors revealed a stake in the company. An activist's aims, whether that's pushing for breakup, M&A, or cost reductions, vary depending on the target. Starboard's turnaround strategy is not yet clear, but Pfizer's share price and revenues have tumbled from the record highs achieved during the pandemic's heights, and Starboard, led by its 52-year-old cofounder Jeff Smith, has a long history of wielding minority stakes to extract board seats and profits from name-brand companies.