Создайте столбец в R для сравнения значений в группе и пометьте как больше (1), меньше (0) или равно (2)

df %>%
  group_by(Round) %>%
  # mutate(Flag = case_when(Score == max(Score) & Score == min(Score) ~ 2, # equivalent
  mutate(Flag = case_when(diff(range(Score)) == 0 ~ 2, 
                          Score == max(Score)     ~ 1,
                          TRUE                    ~ 0))

df %>%
  group_by(Round) %>%
  mutate( Flag1 = replace(rank(Score) - 1, length(unique(Score)) == 1, 2))

  Round Team  Score  Flag Flag1
  <int> <chr> <int> <int> <dbl>
1     1 Team1     4     0     0
2     1 Team2     8     1     1
3     2 Team1     9     1     1
4     2 Team2     2     0     0
5     3 Team1     6     2     2
6     3 Team2     6     2     2
7     4 Team1    14     1     1
8     4 Team2     9     0     0