Effect updates and description changes can be seen here. There are a lot of them.
Beta 7.2 changed Sans drasticly. He no longer kills a card, but instead, takes back his dodging skills. But in a different way. Instead of a certain percentage of dodging each attack, he now has a certain number of times he can dodge, which as of Beta 10.2 is 2. This resets every turn. So he needs to be attacked three times in 1 turn to die. Sans also adds a Gaster Blaster to your hand at the start of your turn, but also the moment you summon it.
Undertale OST - Megalovania Extended
Sans's Theme when played. It starts at 0:16 and ends at 0:23.
Counters
Countering Sans is fairly easy. You can simply Silence Sans with Scarf Mouse or Nacarat Jester, use cards that do X times 1 damage, such as Undyne or Undyne's Spears or place a card that will instantly kill Sans, such as Muffet's Pet, Hyper Goner or Headshot. As you can see, Sans is best countered with the Justice SOUL.
Another way to counter Sans is by placing Clam Girl on the field, as she will return the Blasters to the deck.
Trivia
- Just like any other card, a Shiny Sans gives Shiny Blasters.
- Sans's cost drop to 7G in Beta 10.2 wasn't listed in the Patch Notes.