Meaning of “LasBoss(ラスボス)”

“LasBoss(ラスボス)” is an abstraction for Last Boss(ラストボス) which means final boss (end-stage enemy on video games).
In Japan, Sachiko Kobayashi is called “LasBoss(ラスボス)” because she wears a huge costume when she sing, and it looks end-stage enemy on video games.

Example Conversation

A: Whe I was a child, I watched KouhakuUtagassen on New Year’s Eve.
B: Does it fun?
A: So-so. I did my best to wake up for watching LasBoss(ラスボス) costume of Sachiko Kobayashi.

A: 子供の頃は大晦日は紅白歌合戦見てたなぁ
B: おもしろかったの？
A: まぁまぁかな。小林幸子のラスボス衣装見たくて頑張って起きてた