Mosquito

Mosquito was a former Militaires Sans Frontières member-turned commander of the PF Mosquito Stinger Force after the events of the XOF Trojan Horse operation that destroyed the PMC he formerly worked under.

Biography
Mosquito was part of the MSF Mother Base staff. However, he was kept out of the loop about Paz Ortega Andrade's survival as well as Chico's capture. When the XOF attacked Mother Base, he ultimately survived, although the events greatly haunted him, causing him to break off from his comrades under the paranoia that the group that attacked Mother Base would send a clean-up squad. Ultimately, the years in isolation were unforgiving to him, which caused his sense of loyalty to be screwed up. He eventually learned of a rumor via an anonymous source, that his former commander in MSF, Big Boss, had sold out his comrades so he could go into hiding, and believed the source to be accurate due to Big Boss being absent from Mother Base that day (in actuality, his being absent was because at the time Mother Base had been attacked, Big Boss had to go over to Cuba to save Chico and Paz), so he decided to form his own private force, Mosquito Stinger Force, modeling it after the MSF exactly as it was before the attack and tried to avenge his comrades by attacking the succeeding group Diamond Dogs due to its presumed ties with Big Boss. He deliberately modeled his PF after MSF in every way as he believed it to be the perfect revenge.

In 1984, around the time the Diamond Dogs went to Africa to investigate XOF's activities, he and his PF made their move, holding their new Mother Base's R&amp;D Platform and several Diamond Dogs members hostage, and threatening to kill them if any Diamond Dogs members attempted to set foot onto their platform. Ultimately, his takeover was quelled by Venom Snake, the leader of Diamond Dogs, who had to infiltrate alone without even indirect aid from Ocelot and Kazuhira Miller due to Mosquito's threats, with his PF being captured shortly after his defeat. He was ultimately a victim of disinformation. He can be extracted instead of killed.

Later, Diamond Dogs found the stronghold of the PF Mosquito commanded. There, remnants of the organization were attempting to rebuild it. Venom Snake infiltrated the stronghold and put an end to their plans.

Behind the scenes
Mosquito is a key character in the Main Mission "Retake the Platform" in Metal Gear Solid V: The Phantom Pain. The player can either kill him or capture him to end the mission. If he is captured, Miller will debrief Venom Snake on his identity and motives for attacking Mother Base, and also let Snake decide how to handle him. Mosquito is eventually released from the brig and joins Diamond Dogs. Afterwords, Miller will state Mosquito would be perfect for the newly-formed Security Unit if the player has an internet connection required in order to build Forward Operating Bases.

There are 10 side ops that feature wayward soldiers that had formerly been members of MSF similar to Mosquito, although they were depicted as being more significantly unhinged.

It is stated in the Piggyback official strategy guide for The Phantom Pain that Mosquito is actually the same soldier who helped Miller to escape Mother Base just before it sank into the ocean in Ground Zeroes. The name "Mosquito" is shown in the back of his uniform as well. However, this contradicts what Miller said about Mosquito not knowing why Big Boss left the base and also not knowing that he came back to help Miller and numerous survivors during their battle with XOF. In addition, Miller doesn't recognize Mosquito when talking about him during the mission's briefing.

If the player ignores Miller's emergency call to retake the platform, after a while, Miller will call back saying they've dealt with the attackers, but their leader, Mosquito, was able to escape. However, even after this call, the "Retake the Platform" mission doesn't dissapear from the mission list and it's impossible to progress without completing it. It's unclear if it's a bug but the mission itself doesn't seem to change in any way.

If Venom Snake interrogates Mosquito, he'll ask Snake if he's Big Boss and if he recognizes him.

While inflitrating Mosquito's stronghold in the FOB Event, the player still sees "Diamond Dogs" markings on the equipment and the buildings there. This could be explained by the fact that Mosquito was said to be copying everything Big Boss did. However, it is more likely similar to player-made FOBs where despite their being separate PFs, they all feature the Diamond Dogs logo and this is therefore a non-canon detail.