Last Will was released in 2002 as a part of Starter Deck Yugi but wasn’t banned until the March 2007 ban list. The card aged poorly, as the game became more complicated. This does bring up the question “Why is Last Will banned?”
What does Last Will do?
Last Will was an early Yugioh card, and like a lot of other cards from the era has minimal card text. If a monster on your side of the field was sent to your Graveyard this turn, you can Special Summon 1 monster with an ATK of 1500 points or less from your Deck once during this turn. Obviously, you have to shuffle your deck after searching. A search and special summon in response to a card being sent to the graveyard is pretty good. However, the criteria of the monster had to be under 1500 ATK was supposed to be a limiting factor.
Lower attack monsters got better
The first time the card almost got banned was because of the Magical Scientist FTK. Magical Scientist would be summoned using Last Will, and the Catapult Turtle would then burn your opponent down to 0 life points. This combo could be done without Last Will, but it made the FTK so much easier. Konami was not happy with this deck. However, Magical Scientist was banned. Despite this, Last Will’s luck did run out.
Rescue Cat was the card that was the end of Last Will. Rescue Cat used to be usable multiple times per turn. However, this was later errata’d during the card’s third errata. Also, these monsters were able to keep their effects when summoned. The player would normal summon Rescue Cat then use the effect. This lets you then trigger Last Will which brings out a second Rescue Cat. You would typically bring out Milus Radiant three times plus another beast monster in order to get a +1500 attack per monster.
Last Will was a problem card and aged super poorly. Yugioh at one point was about bringing out high attack beat stick monsters. However, when this card was banned you saw a lot more different strategies.
Can Last Will be unbanned?
No. Last Will was banned before Synchros or XYZ monsters. Players are always sending cards to the graveyard, and decks have too many good cards under 1500 ATK. However, this card could be brought back if it was changed. The card has weird text that kind of lets you summon the monster whenever you want during your turn. The card will have to become a big block of text in order to be unbanned.
If you are interested in more cards that allow FTKs then may I suggest an article on Mass Driver?