These suffixes or enclitics could have a variety of functions, marking TAME, functioning as verbal derivation markers, as inverse markers, relative markers, etc. Only indexes dedicated to core argument marking do not count. The end result has to be a finite verb and cannot, for example, be a deverbal noun or an adverb.
Siamou (ISO 639-3: sif, Glottolog: siam1242)
Siamou is one of many languages with a strong preference for suffixes. In its chapters on aspect, Toews (2015: 99-243) describes six suffixes. Nowhere does the author mention prefixes marking the categories we are interested in. It is coded 1 for this feature.
Pnar (ISO 639-3: pbv, Glottolog: pnar1238)
Pnar only has prefixes according to Ring (2015: 72), who describes prefixes such as the durative marker li- but does not describe any relevant suffixes in the section on verbs (Ring 2015: 145-153). It is coded 0 for this feature.
Abkhaz (ISO 639-3: abk, Glottolog: abkh1244)
Abkhaz has both prefixes and suffixes (Chirikba 2003: 38-39). Non-volitional mood/modality, for example, is marked with a prefix on the verb, while iterative aspect is marked by a suffix. It is coded 1 for this feature.
There is interesting work on the reasons why suffixation appears to be more prevalent than prefixation. So far the best statistics is Dryer (2013) and a potential explanation is given in Himmelmann (2014).
Dryer, Matthew S. 2013. Prefixing vs. suffixing in inflectional morphology. In Matthew S. Dryer & Martin Haspelmath (eds), The world atlas of language structures online. Leipzig: Max Planck Institute for Evolutionary Anthropology.
Himmelmann, Nikolaus. 2014. Asymmetries in the prosodic phrasing of function words: Another look at the suffixing preference. Language 90(4). 927–960.
Chirikba, Viacheslav A. 2003. Abkhaz. (Languages of the World: Materials, 119.) Munich: Lincom Europa.
Ring, Hiram. 2015. A grammar of Pnar. (Doctoral dissertation, Nanyang Technological University)
Toews, Carmela I. P. 2015. Topics in Siamou tense and aspect. (Doctoral dissertation, University of British Columbia)