In Halo 4, 5, and Infinite, Master Chief became a more nuanced, human character.
In spite of the Halo series struggles, 343 deserves praise for adding nuance and characterisation to the ever-beating heart of Halo – The Master Chief. Playing through Infinite, it’s abundantly clear that the events of the current and previous trilogies have irrevocably changed the iconic hero. Hes no longer the blank slate that was previously presented by Bungie. Hes a fatigued, damaged and fallible protagonist, and one who is meandering through currents of grief, while reveling in his newfound agency. Giving the Chief a compelling and meaningful voice was no small feat, and 343 should be proud of that victory.
Source: N4G PC Master Chief Became More Than A Machine In 343's Halo