Explanation:

- By the skin of your teeth: This idiom typically means narrowly or just barely managing to do something. It refers to accomplishing something by a very small margin.

- Option 1: Confident of victory: This phrase suggests assurance in winning or succeeding. It doesn't fit the meaning of the idiom.

- Option 2: Kind towards the weak: Indicates showing compassion or support to vulnerable individuals. Not related to the idiom's meaning.

- Option 3: Determined to strike: Suggests readiness or resolve to take action or make a move. Again, it doesn't align with the idiom.

- Option 4: Just barely: This means managing or surviving with minimal margin. It is the closest match to the idiom's meaning.