Despite his frenetic goalscoring exploits at Paris Saint-Germain, and his strike for Los Blancos in the Super Cup win over Atalanta BC, the Frenchman had not enjoyed the seamless adaptation to La Liga football that many expected him to.
However, Ancelotti has always remained confident that when Mbappe finally lit the blue touch paper in Spain, the World Cup winner would go on the warpath, and he was proven right on Sunday night.
The champions were held goalless in the first half for the third game running, but it was not for the want of trying for Mbappe, who squandered a couple of promising openings before missing an open goal from a Vinicius Junior rebound, although he was offside anyway.
The 25-year-old's inaugural La Liga goal finally arrived just past the hour mark, as he latched onto a delightful backheel assist from Federico Valverde, before completing a quickfire brace from the penalty spot after Vinicius was taken out by Betis goalkeeper Rui Silva.
Mbappe earned a standing ovation and a warm embrace from Ancelotti following a stellar evening's work against Betis, who had their moments in the first half; Abde Ezzalzouli in particular was threatening.
However, Manuel Pellegrini's side never truly looked capable of causing an upset in the Spanish capital, as Real Madrid jump up three places to second in the table - four adrift of perfect Barcelona - while 17th-placed Betis are only above the relegation zone on goal difference and remain winless in 2024-25.
REAL MADRID VS. REAL BETIS HIGHLIGHTS
Kylian Mbappe goal vs. Real Betis (67th min, Real Madrid 1-0 Real Betis)
The drought is over! Mbappe finally scores his first goal in La Liga at the fourth attempt, but this one was all about the exquisite assist from Valverde.
Ancelotti's men had been banging on the Betis door all throughout the second half, and following some neat passing around the Verdiblancos box, Valverde takes out Pellegrini's backline with a gorgeous backheel flick through to Mbappe, who stays composed and fires in his maiden La Liga goal into the bottom corner.
Kylian Mbappe goal vs. Real Betis (75th min, Real Madrid 2-0 Real Betis)
After failing to score in his first seven halves of Spanish top-flight football, Mbappe has two in the space of eight minutes!
Los Blancos' penalty claims are initially waved away as Vinicius is taken out by Silva, with the offside flag denying the Brazilian a spot kick, but replays show that he was clearly on.
The referee goes to the pitchside monitor and points to the spot, and after a brief pause, Mbappe nonchalantly sends Silva the wrong way to rubber-stamp a morale-boosting win for the Spanish champions.
MAN OF THE MATCH - KYLIAN MBAPPE
A special shoutout to that outrageous assist from Valverde for Real Madrid's first goal, which capped off a classy display from the Uruguayan, but when Los Blancos needed Mbappe to step up, step up he did.
Ridding himself of the La Liga m on his back, the Frenchman got into several good positions but was just unfortunate - and a tad wasteful - in front of goal, seeing several shots blocked before clinically dispatching both of his second-half goals.
Unless you are Didier Deschamps, the international break could not have come at a worse time for Mbappe, who must surely be relishing his next appearance in the famous white strip.
REAL MADRID VS. REAL BETIS MATCH STATS
Possession: Real Madrid 60%-40% Real Betis
Shots: Real Madrid 21-11 Real Betis
Shots on target: Real Madrid 7-2 Real Betis
Corners: Real Madrid 7-3 Real Betis
Fouls: Real Madrid 9-17 Real Betis
BEST STATS
WHAT NEXT?
Both sides will return to domestic duty following the international break, as Real Madrid travel to Real Sociedad on September 14, where they are still likely to be without the services of Jude Bellingham but will at least have an off-the-mark Mbappe in their ranks.
The day before the champions are back in action, Betis take on newly-promoted Leganes at home on Friday, September 13, in a game that marks the return of La Liga football.