As soon as you do, your opponents are effectively forced to block that creature every turn, and the deathtouch buff guarantees you destroy whatever you touch
If it gains 8 life all by itself with double strike, the reanimator aspect gets really powerful
Avacyn breaks games in seconds
It provides a true zero-mana option for countering noncreature spells, only costs a single mana more than Negate itself when hardcast, and even exiles the target to boot
There are tons of ways to get lands into your graveyard in green, whether its sacrificing, cycling, or milling (including dredge), and when the melded Titania, Gaea Incarnate enters the battlefield, any lands in your graveyard are put on your battlefield tapped
In either case, the deck needs tricky defenses to get to that point, since its creatures can't stand up to the format's biggest beaters