Board Thread:General Discussion/@comment-4504826-20160419213858/@comment-39394247-20190611161814

If you attack Glad Dummy, he does not die, and a harder version of the Mad Dummy fight occurs. You have to get 600 hits on the dummy to kill him, and when his HP is down to 300, the dummy bot phase begins.

Undyne:

If you make a weak hit on Monster Kid, Undyne will not die from that attack, and you have to fight her for a few turns after before she turns into Undying. Normal Undyne's attacks are like (normal mode) Undying's, and the real Undyne the Undying is way more difficult, with Undyne actually having 99 ATK (20 damage per hit) and 99 DEF (with no damage restriction), as well as the same HP as normal Undyne (1500, as opposed to 1095).

Once Undyne the Undying's HP is reduced to 0, you have to fight her for 10 more turns as she melts. Her ATK and DEF increase rapidly during this phase, so that by the 5th turn, any FIGHT will result in a MISS, and on the 9th turn, one hit will instakill you. On the 10th turn, she has melted fully into an amalgamate, and the only way to end the battle is to flee. You don't get any XP or G from this fight, but your LV is likely going to be 13 at the start (more encounters).

In Pacifist/Neutral, she catches up to you quicker when you flee, and she has 20 DEF and 50 ATK (10 damage per hit). You also have to fight her before and after you befriend her for 5 turns, and these attacks are comparable to Undying's, but still only do 10 damage. You can also prevent her house from burning if you refuse to turn the heat up 4 times.