An incomplete list of teams better than the 2012 Chiefs:
2008 Lions (0-16) - had a halftime lead, week 6.
1982 Colts (0-8-1) - had a halftime lead, week 2.
1976 Buccaneers (0-16)- had a lead in the first quarter in week 3.
1960 cowboys (0-11-1) - lead after Q1, week 1.
1944 Brooklyn Tigers (0-10) - lead after Q1, week 5
1944 cardianls/Seelers (0-10) - led after Q3, week 1.
1943 Cardinals (0-10) - had a Q2 lead, week 1
1942 Lions (0-10) - had a Q2 lead, week 3
that's as far back as box scores go....no data readily available prior to 1940. It's possible no team has played 7 games w/ having a lead ever, but that can't be verified.
The 2011 Charlotte Bobcats
won game 1...the worst ever NBA team held a lead during game 1, so they are better than the Chiefs.
The worst hockey team of all time, the 1974-75 Washington Capitols,
won game 4, so they are better than the Chiefs.
The worst baseball team of all time was the 1899 Cleveland Spiders.
They won game 5, so they are better than the Chiefs.
Right now, IMO it's fair to say that the Chiefs are possibly the worst team of all time, in all of sports.