Practice and timing are everything....if everyone trains to fight the same way, then you'd have the UFC or Boxing. Your opponents know what is coming and how to counter it...practicing a spinning backfist for example, training for it with differing opponents will provide you with a higher chance of landing than someone who goes for the high percentage shots.
It all depends on your skill set, mind set, and who you are as a martial artist. A head kick coming from a 300 lb man would something I wouldn't expect, hence my focus would be at preventing him from taking me down, landing a huge hay maker, or cornering me where I couldn't use space to my advantage. Again, if he trains for it, has the coordination and speed to pull it off, it would be devastating.
"if its ok for shaolin wuseng to break his vow then its ok for me to sneak behind your house at 3 in the morning and bang your dog if buddha is in your heart then its ok"-Bawang
"I get what you have said in the past, but we are not intuitive fighters. As instinctive fighters, we can chuck spears and claw and bite. We are not instinctively god at punching or kicking."-Drake
"Princess? LMAO hammer you are such a pr^t"-Frost