表反对某一观点：
I disapprove that…
I disagree with this viewpoint for three reasons:…
I do not personally believe that…
To those who argue that …,I ‘d like to point out that…
However, I am not a believer of the argument that the computer may in the future take the place of teachers in the teaching field.
The worst aspect of this phenomenon, in my opinion, is that…
While compared with A, B may not be significantly important.
However, its strenghs are dwarfed by its weaknesses.
In fact ,… can cause a lot of problems, such as…
Altough, it may seem a logical solution, taking this easy way out may cause as many problems as it solves.
However, with the best wishes in the world, we may not always reach our goals successfully.
On the minus side…
It is pointless to do sth.