This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / World in Conflict
After Captain Bannon's Heroic Sacrifice in World in Conflict, there's a short cutscene where his mother listens to the last voice message from him. It narrates how good a soldier he was recently, encourages her that the war soon be over, and says he is out of danger for now. Then you realize that she has been crying all along, meaning that the news already reached her...
When Bannon contacts Colonel Sawyer to describe the advance and tries to apologize for his actions in earlier battles, Sawyer tells him that he's honored to have served with Bannon. Death may equal redemption in this case, but despite Bannon being The Scrappy for much the story, you can't help but feel the emotion in Sawyer's words. His silence immediately afterwards is sobering.
Commandant Sabatier is speaking over the telephone with his heavily pregnant mistress who is openly crying as she explains to him that she dreamed he was killed in battle, to which he immediately assures her he is alive and well, and that they will soon reunite. Such reunion was not to be, as Bannon deserts him to aid the final assault on the Soviet HQ in France, during which Sabatier is overwhelmed and killed in an ambush.
Seeing Seattle in ruins drives home how terrible war is.
The Searching for Survivors trailer follows a tank commander and a nurse surveying the ruins of Pine Valley, where the commander reminisces on his former life here and the day he proposed to his wife there, against flashbacks of the battle that sees it destroyed in a tactical nuclear strike; his somber, distant tone as they depart to return to battle sums up the tragedy of losing everything you ever knew in war.
The briefing for the defense of Cascade Falls happens in an elementary school classroom, with an alphabet poster above the chalkboard Sawyer is drawing tactical diagrams on. That really helped the impact of this war hit home... and then you consider that nearly EVERY war occurs in someone's home, in their schools, their streets...
Parker remarks on seeing a destroyed swing set standing right next to a crater where a Soviet bomb had earlier been dropped; his somber account of what he is witnessing reminds us of the nightmare they are facing and the bloodshed that will inevitably follow.
The mission "Aftermath" really showcases the utter devastation of nuclear warfare, leaving nothing but a scarred, almost lifeless landscape in its wake. Captain Webb's mourning of Bannon and his disbelief at what has just happened in Cascade Falls really sums up the enormity of the attack and the hopelessness one may feel to bear witness to it and live to tell of the scenes that follow.
The President's decision to obliterate the Soviet forces in Seattle in a nuclear strike to prevent the Chinese Navy from coming ashore in the event that Sawyer's men cannot eliminate the Soviet presence first; The President and the general talking to him clearly hate themselves for possibly having to do the unthinkable.
Even moreso if you fail the last mission; From the mission debriefing, you discover that even after the nuclear strike destroys Seattle and the enemy with it, the USSR commits to nuclear warfare as the U.S. has already willingly done on its own country twice. "And the rest is history".....
The late storyline of the Soviet Assault expansion was just horribly sad. Where to start?
Sometime during the raid near Murmansk, Captain Malashenko learns that his wife and daughter were killed by a NATO raid. The kicker? It's implied that they were among the civilians that Bannon massacred. This eventually leads to Malashenko's increasing Blood Knight and Knight Templar tendencies, as well as his implied death in Seattle.
Orlov's fate. He's a generally decent guy who cares about the soldiers under his command, and often does his best to prevent needless bloodshed. He's killed by his own nephew for ordering a retreat from the United States, as he knows that the invasion is hopeless at this point.
The final half of the last mission, Fratricide, in which Lebedjev and Romanov assume control of Orlovsky's unit and mounts a desperate Hold the Line defense against the vengeful American forces to protect a convoy of wounded soldiers. Orlov has been killed, and Malashenko has taken his men to Seattle, where they will likely be killed in the battle. Most heartwrenching was the music playing in the background at the last stand, and Lebedjev's calm comments highlighted the hopelessness of the battle.