Near-infrared (NIR) photodetectors are critical for numerous applications including optical communications, biomedical imaging, and night vision. However, conventional photodetectors suffer from an inherent trade-off between high photoresponsivity and fast response speed, alongside limitations in flexibility, long-term stability, and operational temperature range. To overcome these challenges, a photodetector based on atomically-thin platinum diselenide (PtSe2) film is proposed in this work, which combines the photoconductive gain of PtSe2 with rapid carrier separation and extraction at the metal-semiconductor junction. Through the synergy of these two mechanisms, it achieves ultrahigh photoresponsivity (132 A/W) and ultrafast response speed (37.5 ps), effectively resolving the traditional performance trade-off. We further realize the integration of large-area, uniform device arrays (over 1100 units) on flexible mica substrates and demonstrate high-quality imaging capability. The photodetector arrays also display outstanding flexibility, excellent long-term stability and a record-wide operating temperature range from -150 °C to 400 °C. This work highlights the great potential of atomically-thin PtSe2 for developing next-generation ultrasensitive, high-speed, robust, and flexible optoelectronic devices.