library(stringr)
text <- 'tessst gfvdsvs bbbddsa daxz'
new <- unlist(str_extract_all(text, "\\p{L}*(\\p{L})\\1+\\p{L}*"))
i <- max(nchar( unlist(str_extract_all(new, "(.)\\1+")) ))
new
i
bGlicmFyeShzdHJpbmdyKQp0ZXh0IDwtICd0ZXNzc3QgZ2Z2ZHN2cyBiYmJkZHNhIGRheHonCm5ldyA8LSB1bmxpc3Qoc3RyX2V4dHJhY3RfYWxsKHRleHQsICJcXHB7TH0qKFxccHtMfSlcXDErXFxwe0x9KiIpKQppIDwtIG1heChuY2hhciggdW5saXN0KHN0cl9leHRyYWN0X2FsbChuZXcsICIoLilcXDErIikpICkpCm5ldwpp