Greater Stone Spirit can't be blocked by creatures with flying.
{2}{R}: Until end of turn, target creature gets +0/+2 and gains "{R}: This creature gets +1/+0 until end of turn."
Creatures with the Reach ability (such as Giant Spider) can block this because they don’t actually have Flying.
After Greater Stone Spirit’s activated ability is activated, the affected creature gains an activated ability that only that creature’s controller can activate.