With Club World Cup reaching the final matchday of the Group Stage, it is highly likely that some teams will be tied in each group, thus needing to use tiebreaks to decide the order, as only the best two teams in each group will qualify. And unlike other competitions, goal average is less important here, as most tiebreaker rules only apply between the teams involved in the tie.
These are the tiebreaker rules for Club World Cup in group stage. The traditional goal average only applies as the fourth rule:
Thus, it doesn't really matter if you scored two, four of ten to the worst teams in each group, as the goals that matter in case of a tie are those in the head-to-head with the other team.
That's particularly interesting in the case of Group B, with the possibility of a triple tie between Botafogo, PSG, and Atlético de Madrid. In the case that happens, it doesn't matter how badly they thrashed Seattle Sounders...
Group B
On Monday, June 23 at 21:00 CEST, 20:00 BST, PSG plays against Seattle and Atlético de Madrid plays against Botafogo. In the likely scenario that PSG beats Seattle, and even if Atlético de Madrid beats Botafogo, tying all three with 6 points, Atleti would be left out unless they win with a three goal margin to the Brazilian club, because Atleti's goal difference is -4 (only goals against teams involved in the tie are counted for the tiebreak, currently, the four goals they suffered against PSG).
In short, Atlético de Madrid needs to beat Botafogo by three goals if PSG wins Seattle. If PSG draws against Seattle, Atleti would need to win by two goals. Only if PSG loses to Seattle can Atleti afford to win by any margin or even draw against Botafogo.