As of my last knowledge update in September 2021, opinions on the "worst rule" in football (soccer) can vary widely among fans, players, coaches, and experts. Rules that are considered the "worst" can change over time based on the evolution of the game, controversies, and shifts in perspectives. Here are a couple of rules that have garnered criticism in the past:

VAR Implementation: The introduction of the Video Assistant Referee (VAR) system has been a subject of controversy. While the intention behind VAR is to improve the accuracy of refereeing decisions, its implementation has led to debates over how and when it should be used. Critics argue that VAR can lead to delays in matches, disrupt the flow of the game, and still result in subjective interpretations of incidents.

Handball Rule Interpretation: The handball rule has been a point of contention for years. The interpretation of what constitutes an intentional or accidental handball has been inconsistent, leading to confusion among players, officials, and fans. The rule changes in recent years, aimed at reducing subjectivity, have sometimes led to unintended consequences and controversial decisions.

Offside Rule and Marginal Calls: The offside rule has evolved over time to incorporate technology like VAR for close offside decisions. However, even with technology, marginal offside calls can be challenging to make accurately. Critics argue that these calls can be too fine and lead to goals being disallowed for seemingly minor infractions that don't significantly impact the game.

Penalty Kick Encroachment: The rule that requires players to stay outside the penalty area until the kicker strikes the ball has been criticized for being inconsistently enforced. Some argue that defenders often encroach during penalty kicks, leading to retakes and additional disruptions.

Diving and Simulation: While not a rule in itself, the issue of diving (simulation) and players attempting to deceive referees by exaggerating fouls has been a source of frustration for many. The challenge lies in determining when a player is genuinely fouled and when they are attempting to deceive the referee.

It's important to note that discussions about the "worst rule" are often subjective and influenced by personal preferences, experiences, and the current state of the game. The rules of football are continually reviewed and updated by governing bodies like FIFA, UEFA, and national associations to address issues and maintain the integrity of the sport. Rules can change to adapt to the evolving nature of the game and the concerns raised by players, officials, and fans.