Before Asgore's death he was very helpful and kind just like Undertale Asriel, but soon everything changed he died and transformed into a buttercup and went by the name Butter (He's still bad with names just like Undertale Asgore). At first "Butter" was kind and helped everyone but soon he became evil and was tired of kindness. He murdered everyone and then reset like nothing happened with his new found powers. When Liam (The main protagonist) does Pacifist Asgore tries to murder him as fast as possible, however Chara prevents that and saves Liam.
Asgore wears a yellow sweatshirt and has small horns on his head. On the shirt there is a beautiful buttercup that looks almost realistic. After Asgore's death he become a buttercup and just like Undertale Asriel his appearance changes. He looks very similar to Flowey except that he has two layers of petals. His OMEGA form is the same as Flowey's but his TV Screen has funny and short animations playing, he did this to distract Liam so he could kill him. His final form is the same as Undertale Asriel's except that it has his head instead of Asriel's (I hope this description helped because I can't draw for shit)
Asgore was the first son of Asriel and Chara. Chara was the first human to fly up and unlike monsters she aged and soon she was the appropriate age to marry someone. She fell in love with King Asriel and they were married, soon Asgore was born with one half of his soul being part determination. As the years went by they lived happily but Asgore found out that they were trapped underground because of the humans. He was furious. 2 years later Asgore was 10 and his younger sister was born, her name was Toriel, once Toriel became 7 Asgore told her about humanity trapping them, so he came up with a plan to destroy them all, he said that he would kill himself so Toriel could absorb his soul to destroy the humans. Toriel was unsure about this but agreed and absorbed Asgore's soul. The outcome was horrible, Toriel refused to fight and went back into the Underground, injured by the humans. Soon her dust spread because her soul was a monster soul and was not part determination like Asgore's. Toriel became a ghostly creature and Asgore became a buttercup. Enraged, Asriel declared war and said every human that falls down would be killed. Chara was mad at Asgore and left him alone. She then returned to the Ruins never to be seen again by other monsters (Except Froggits etc.).