To check if a creature is a legal target for the second mode, put the cards side-by-side, right side up, such that if you had a ruler, the top of both cards would be lined up against it. If any part of that creature's head is higher than the bottom of the bar (that is, if it would hit the bar), the creature is a legal target.
If there are multiple creatures in the art, only compare the one that represents the actual creature on the card. For example, Tarmogoyf (MMA) has the tarmogoyf itself and an elk in the art, and you need only consider the tarmogoyf.
If there are multiple creatures in the art that each match what the card is representing, then you can target that creature if any of them has any part of its head higher than the bar. For example, Llanowar Elves (M19) has three figures in its art, all of whom are Llanowar elves. The creature can be destroyed if any of those elves has a part of their head higher than the bar.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Leonardo Santanna
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
Only a creature's head counts. Other body parts (such as tails) being above the bar doesn't make a creature a legal target. If a creature is wearing a hat on its head, treat the hat as part of its head.
