Outermost boundaries with 限界
限界 combines kanji for limit and boundary.
Dictionary Definition
物事の、これ以上あるいはこれより外には出られないというぎりぎりの範囲、境。
The extent or boundary of a thing, beyond which it cannot go any further or outside of.
Goo Dictionary
Examples
At one's limit with 限界

Mina wants to hurry and eat her lunch, as she’s very hungry. Yukari reminders her they still have one more class first.
- ミナ:
- 「もう限界だよ!こんなんじゃ次の授業、集中できないよー。」
- “I'm already at my limit! As things are, come next class I won't be able to concentrate.”
The limit of teamwork with 限界

On a snowy day, Alicia starts making a snowball. As it gets bigger, Akari joins in. They continue to roll the snowball until it grows too big for them to keep pushing. At that moment, a random person passing by notices their effort.
- 灯里:
- 「アリシアさん… 二人の力ではこれが限界かと」
- “Alicia... This is the limit of what we can do together.”
- 男:
- 「おおっ 大きいな」
- “Oh! That's a big one.”