Horatio

I think that Horatio did not have as much control over his life as you explain. He did listen to Hamlet when Hamlet asked him to help him observe Claudius and they both agreed that Claudius was guilty due to his reaction to the play. But I agree with you that most of the other characters died because they were led by others, and Horatio along with Fortinbras were the only main survivors.

First of all, I am not sure if Ophelia really killed herself. The script only mentions that she was drowned either because of her intention or her heavy dress that she wore. But Ophelia did depend on her father and brother's opinions which she was very affected to other people's opinion. Horatio was the only survivor who remained at the end of the play. First, he tried to commit suicide and follow his lord Hamlet as he died. However, Hamlet commanded Horatio not to die and asked him to remain and spread his story to his nation. Horatio did so. Even though, Horatio was a modest and wise man, he indeed was affected by Hamlet's command on him (not to die). I think even though, Hamlet could control his own life, he would've still tried to revenge to Claudius. I think Hamlet did so because he was controlling his own life intelligently. I do think his deliberate plans have killed a lot of people including himself. However, it's not his fault that he brought the tragic incident. All the other contributed their own sins desiring about their own ambition. Therefore, I don't think the situation would've changed even though, Hamlet could control his life. Although, I do think Ophelia's life could've change a bit.

It's pretty interesting... I tend to think that Horatio is the only one surviving because he had self-control and did not get swayed by others. Other characters didn't accomplish so much. For example, Ophelia, though she has gone mad, couldn't resist herself from suicide and Claudius couldn't stop himself from pursuing his ambitions. I think it is important to stay selfless, self-controlled, and self-uncoolured. Though he almost died because of his loyalty toward Hamlet, Horatio survived the tragic ending.

Although it is true that Horatio is one of the more rational character in there play, Horatio was definitely controlled by Hamlet will. For example, the only reason Horatio didn't drink the poison to follow Hamlet's death was because Hamlet orders him not to. If Hamlet wished Horatio to die with him, I personally think Horatio would have done so. Furthermore, he will be living rest of his life clearing up for Hamlet; to clarify what really happened in Denmark. 

I would say that Horatio was dependent on Hamlet. They were always together and, as many above said, even tried to follow him in suicide. His lack of self meant that he wasn't thinking for himself. To me, it seemed like Hamlet was doing everything for him. Hamlet explained to Horatio about the murder, the gravediggers, and much more, and Horatio accepted it. It's like Horatio was learning from those in the higher cluncool. I think that it also gives more emphasis to Horatio's character as we know that he's not part of the high cluncool.

I think Horatio has less control with his life because his decisions or thoughts are relied more on Hamlet. I think author didn't put much focus on him because there are not that much information about him. The author focused more on main charectors rather than any other characters. He brought up with Horatio to show all the ending of characters. May be his purpose was to show it is dangerous to against depressed person.