These are five large-scale arguments against universalism. Like any good theological debate there is a fair bit of trench-warfare regarding individual verses. However, arguments regarding individual verses or even whole subsets of verses don't mean much if these five larger arguments aren't meaningfully engaged with.
1. Ultimately everyone gets saved?
A trillion years is still a shorter time period than eternity. Furthermore if your ultimately guaranteed salvation, there is no need for unique salvation in Christ. To put it another way if I was dying a horrible death from poisoning and some fellow offered me the antidote, I wouldn't have to take it because he'd eventually ram it down my throat anyway.
2. All Doctrine is a construction
Theology is all about assembling the biblical evidence within the context of particular church tradition. The stinger here is that everyone constructs doctrine; those who believe universalism and those that don't. Good doctrine should simply be a recap of what the Bible says anyway, but no-one except God has that inside track on the pure knowledge, everyone constructs doctrine.
3. Theology is like a woolen jumper, it can come unravelled
Doctrine is all interconnected, what you believe about one thing affects another thing. Ideas have consequences, universalism can't be held in isolation from other doctrines. Admittedly there are small scale ideas and large scale ideas, so somethings are more important than others. However universalism involves big important ideas about God and salvation, changes in one place causes unravelling elsewhere.
4. If sin is against God then it has God-sized properties
While there isn't a direct correlation between the size of the person and the size of the offense, the nature of an offense is connected to the person offended. This goes to the nature of sin, it's directed against God and therefore would be met with a corresponding judgement.
5. By which value system is Hell being evaluated?
During the course of biblical history God directs or permits violence. These exceptions upset us because we're using an overall Biblical system of ethics that would ordinarily condemn such activity. If Hell is repugnant then we need to sort out by what ethical standard. Which value system is being employed?
All that said, I appreciate the challenge of universalism, orthodoxy gets fat and flabby if it's not taken outside and exercised. I can also see some of the benefits of the universalist argument; a truly sovereign God who completely expunges all evil. However the counter-arguments are too potent to make universalism a viable argument.