Can Ranata score 1 point win the game when it's your turn?

Yes, you can win the game by using Renata Glasc, Mastermind's activated ability to score your final point, provided you have more points than any opponent.

Ruling

According to Rule 466.1.a.1, points gained from sources that are not "Conquer" or "Hold" are not beholden to the special restrictions that apply to those two methods, such as the requirement to score both battlefields in the same turn when conquering for the final point. Because Renata's ability is an activated ability that grants a point directly, it is not subject to those specific conquer/hold restrictions.

How the Ability Works

1. Activated Ability: Renata Glasc, Mastermind has an activated ability: [4] [C] [C] [C] [C] , [T] : Score 1 point.
2. Using the Chain: According to Rule 377.3, activated abilities use the chain. When you activate this ability, you declare it, pay the costs (4 energy, 4 power, and exhausting Renata), and place the ability on the chain as a pending item.
3. Closed State: Placing an activated ability on the chain creates a "Closed State" (Rule 377.3.a.1). During this time, players have the opportunity to play [REACTION] cards in response to the ability before it resolves.
4. Resolution: If no further actions are taken, the chain resolves (LIFO). When the ability resolves, you score 1 point.
5. Winning the Game: Per Rule 467, if you have accrued points greater than or equal to the Victory Score (8 in a 1v1 game) and have more points than any opponent, you win the game. Since this point is gained via an activated ability, you win immediately upon scoring the point if it brings you to 8.

Note: I could not fully verify this ruling against the retrieved rules, as the specific card text for 'Renata Glasc, Mastermind' was not present in the provided context.