Jeremy Grantham says ‘easiest leg’ of stock-market bubble burst is over. What’s next.

Think the bear market in U.S. stocks has been rough? The hard part may still lie ahead, according to longtime stock market investor Jeremy Grantham.

The legendary co-founder of Boston-based investment firm GMO argued in a Tuesday paper, cheerfully titled, “After a Timeout, Back to the Meat Grinder,” that “the first and easiest leg of the bursting of the bubble we called for a year ago is complete.”

The…