Foreman has the all time record for best win/ko ration of any lineal champ. V. Klitschko's ratio is actually higher, but he's not viewed by many as a lineal champion. Frank Bruno was another one, as was Marciano. If you venture beyond the rank of champion, you'll find guys like Shavers, Don Steele and Alex Stewart, the last two are not names commonly mentioned by most fans.
Marciano has the highest knockout percent of any lineal champ, Foreman is 2nd, Foreman's comeback lower his knockout percent. Only 1 heavyweight champ has a 100 percent ko rate. Henry Hen Pearce. 7 wins, 0 loses, 7 knockouts. And 7 fights. Heavyweight champ from 1803-1805.