Опция в base R
с rowsum
rowsum(+(df1$diff > 5), df1$individual) != 0
или с by
by(df1$diff > 5, df1$individual, any)
data
df1 <- structure(list(individual = c("A", "A", "A", "A", "B", "B", "B",
"B"), val1 = c(32L, 36L, 28L, 26L, 65L, 58L, 57L, 54L), val2 = c(36L,
28L, 26L, 26L, 64L, 59L, 54L, 51L), diff = c(-4L, 8L, 2L, 0L,
1L, -1L, 3L, 3L)), class = "data.frame", row.names = c(NA, -8L
))