Certainly you can try to avoid pain. And very likely you can do Aikido with almost no pain if you are practicing with people who trained it for a long time and had that goal in their training. But I often see very experienced participants pinning each other down and slowly twisting their joints until there is a painful expression on the face of the receiving partner becomes visible and s/he taps out. When asked s/he will report to have felt pain. The inflicting partner will report to have consciously willed to cause pain to the receiving partner. I remember similar events in differed Dojos across different styles. I tried to list situations were similar behavior can be observed in the course of our lives outside of Aikido and to see in which respects the situations differed from the one in an Aikido training.