The Chiefs' defense was just as awful. Why should they be let off the hook?
Allen was just as incredible and amazing as Mahomes. Why can't he get another shot to respond?

If the Bills had won the toss and scored that TD, the same would be true vice-versa.

The fact that an all-time classic, extremely important PLAYOFF game with high stakes can come down to a freaking COIN TOSS is total bullshit.

Exactly this. 

Nobody's saying the Chiefs weren't worthy of the win...but we all know that like 90% of every overtime game in the NFL simply goes to whichever team wins that damn coin toss. It's just not particularly sporting.

Yes, as I said the OT rules are terrible and need to be changed. It was quite clear that both had awful defense in this game ( a point nobody is disputing). All we can hope for is that the NFL changes the rules next season (although I have my doubts they will).

The rules should be structured around getting the first STOP, not the first score.
This should be the OT rules:

Each team gets at least one possession UNLESS the opening drive results in a defensive score - (Safety or a pick-6.)

If the opening drive results in an offensive score (FG or TD), then:
- The opposing offense will get a chance to tie or take the lead.
- If that opposing offense is successful in tying or taking the lead, then the other team's offense gets the ball back with a chance to do the same.
- This process will continue until:
       A) The first successful defensive stop or turnover. (If the game is still tied, the next score wins it.)
       B) Time expires.

If the opening drive results in a successful defensive stop with no score, then:
- The next score wins it. Just like it is now.

This may result in more ties in the regular season, since you have a 10:00 time limit, but who cares. That's what those teams get for not getting the job done.

Once you get to the playoffs, you can have one of two options:

No Game Clock. Just the Play Clock. 40 seconds to get off a play. That's it.

OR

If the 10:00 time limit expires: Go straight to FG kicks. Similar to soccer.
Start at extra point distance, and then keep going 5 yards back for each successful kick.
IF:
- The first FG miss happens with the score tied, then the next make wins it.
- The first FG miss happens with that team behind, Game Over.

For example: If the Bills and Chiefs went to FGs and Butker misses the first one with the score tied, if Bass makes the one after that. Ballgame: Bills win.
But if the Chiefs are ahead and Bass misses his field gold. Ballgame: Chiefs win.

Make it so that the DEFENSE and SPECIAL TEAMS are the ones that has to come through, no the offense.

Because Football is a three unit game. Offense Defense and Special Teams. 
The bills had a chance to react on special teams and defense and they didn’t. 

Obsessed with Pittsburgh much?  You're taking it to personally that Cleveland has a 9-38-1 record against the Steelers since the Browns re-entered the league as an expansion team in 1999 (the real Cleveland Browns are in Baltimore and have won 2 Super Bowls as the Ravens).

Meanwhile, I was happy to see Green Bay get eliminated this weekend.  All that crying that Aaron Rodgers did about Matt LaFleur taking the ball out of his hands and costing the Packers the NFC Championship last year, he throws 0 TD passes and only produces a total of 3 points for the rest of the game after the Packers opening drive TD.

After the Bills collapsed last night unable to hold leads with both 1:54 remaining and 13 seconds remaining, I was thinking the Bengals don't have a chance against the Chiefs next weekend.  Joe Burrows did scorch them for 400 yards and 4 TD's earlier this month, but that was at home.  And the Bills stomping KC earlier in the season (at Arrowhead no less) had no bearing on last night's game.  It should be an interesting conference championship weekend.

Of the possibilities in play:

- Los Angeles Rams could become the 2nd consecutive team to play in the Super Bowl in their home stadium.  Tampa Bay won last year at Raymond James Stadium.  This year's Super Bowl is being played at SoFi Stadium.

- Kansas City Chiefs and San Francisco 49ers could be a Super Bowl rematch from Super Bowl LIV.  Patrick Maholmes and Jimmy Garoppolo would also be a head to head QB rematch.  Previous QB rematches include:  Terry Bradshaw vs Roger Staubach (Steelers defeated Cowboys, Super Bowls X and XIII), Troy Aikman vs Jim Kelly (Cowboys defeated Bills, Super Bowls XXVII & XXVIII), Eli Manning vs Tom Brady (Giants defeated Patriots, Super Bowls XLII & XLVI).  So far no losing QB came out on top in the rematch.

- Cincinnati Bengals vs San Francisco 49ers would be the 3rd Super Bowl meeting of the 2 franchises.  The Bengals lost Super Bowls XVI and XXIII to the Joe Montana and the 49ers (Bengals were led by 2 different QB's, Ken Anderson and then Boomer Esiason).  The Pittsburgh Steelers and the Dallas Cowboys faced each other 3 times with Terry Bradshaw leading the Steelers to victory in the aforementioned Super Bowls X & XIII, while the Neil O'Donnell led Steelers lost to Troy Aikman and the Cowboys in Super Bowl XXX.

- The Kansas City Chiefs could be the 3rd team to appear in 3 consecutive Super Bowls.  The Buffalo Bills appeared (and lost) in Super Bowls XXV (vs Giants), XXVI (vs Washington), XXVII (vs Cowboys), & XXVIII (vs Cowboys).  The New England Patriots appeared in Super Bowls LI (defeating the Falcons), LII (losing to the Eagles), and LIII (defeating the Rams).  No team has ever won 3 consecutive Super Bowls, and with the Chiefs having already lost to Tampa last year, that remains true whether KC gets back to the Super Bowl this year or not.

It didn't come down to a coin flip.  The Bills had every chance to stop the Chiefs in overtime.  It was not guaranteed that the Chiefs were going to score a touchdown.  Just like it was not guaranteed that the Bills would have scored a touchdown if they got the ball first.

For the current overtime format, the record for teams that win the coin flip in overtime: 86-67-10

So win 52.8% of the time, lose 41.1% of the time, tie 6.1% of the time.

Personally, I think both teams should get at least 1 offensive possession, and then the game turns to sudden death after that.  But I don't see it happening.  The Chiefs lost to the Patriots in the 2018 AFC Championship game exactly like this.  The Chiefs proposed changing the overtime rules after that season so that both teams would get possession, and it didn't even get enough support to get a vote.

11 playoff games have gone to OT since the 2010 rule change.  10 of the 11 teams who won the coin toss went on to win the game.  7 of those 10 teams won the game on their first possession.

NFL overtime history: Revisiting the 11 playoff games that have gone to OT since 2010 rule change