p > pf > f
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Other examples abound, although I don't want to just give a long list.
One salient example is the affrication which accompanied palatalization in Romance. In various environments in various languages this took the various forms:
k,t → tʃ,ts → ʃ,s,θ
g,d → dʒ,dz → ʒ,j,x
Affrication very often accompanies palatalization, for example in Japanese t,d → tɕ,dʑ/ts,dz before i/ɯ; or English t in question, nature. I understand similar processes have occured in Finnic.
However, it is notable that the diachronic stop->fricative lenition does not always have an affrication stage, and can go right from stop to fricative. An example of this is the first Germanic consonant shift, Grimm's law:
bʰ → b → p → f
dʰ → d → t → þ
gʰ → g → k → h
gʷʰ → gʷ → kʷ → hʷ