Is it obligatory to emphasize letters—especially the hamza and the kaf—in prayer, or is it sufficient to pronounce them softly?

The questioner is experiencing obsessive thoughts, and he should ignore them and turn away from them. The religion of Allah is ease, and over-exertion and extremism are not part of the religion. One must pronounce the letters and articulate them from their proper points of articulation naturally, without excessive emphasis or over-exertion. If a person speaks normally and there is nothing preventing correct pronunciation, then their recitation is generally correct. However, if there is something preventing correct pronunciation, they are not held accountable for it, as Allah does not burden a soul beyond its capacity. It is not prescribed to pronounce letters with force and over-exertion, because excessive emphasis can spoil the pronunciation of the letter. A letter that is to be emphasized should be emphasized without exaggeration, and a letter that is not to be emphasized should be read without emphasis.