How is an Ish Chesed "Gomel Nafsho"?
Rashi: A Chasid bestows good to his relatives.
Ta'anis 11a (according to Rashi there): One who is able to bear a fast, he bestows good to his Nefesh via fasting 1 .
Ta'anis 11a (according to Tosfos there): One who is cannot bear a fast, he bestows good to his Nefesh via eating.
R. Yonah #1: He aggrandizes his Nefesh through good habits and intermediate Midos 2 , like one raises a small body - "ki'Gmul Alei Imo ki'Gmul Alei Nafshi" (Tehilim 131:2). The middle Midah in bodily pleasures of an Ish Chesed is to separate his body from desire, and satiate (fulfill them) with what is needed to sustain the body.
R. Yonah #2: This discusses stinginess. A person benefiting his Nefesh is included in the way of Chesed. He intends to benefit it from his hands' toil, as is needed to sustain health. Man is rewarded for benefiting his Nefesh, if he intends for its success, and not for bodily pleasure.
Malbim: Ish Chesed is one who normally does Chesed with everyone, without hope for reward, and without arousal of a Midah of mercy, compassion
Rashi (11): Gomel is refraining [from food and drink], like [weaning] - "b'Yom Higamel Es Yitzchak" (Bereishis 21:8).
In general, the proper Midah to between the two extremes (Rambam, Hilchos De'os 1:4).
Why does it say "v'Ocher She'ero Achzari"?
Rashi: A cruel person troubles his relatives.
R. Yonah: One who troubles his body, and starves and afflicts himself, is called cruel, just like one who does evil to others. Afflicting the body decreases bodily powers and sabotages it from doing its work; it will not succeed in Chachmah and Avodas Hashem.
Orchos Tzadikim (Sha'ar ha'Achzariyus): There is no Chesed in a cruel person. Malbim - Achzari is the opposite of Ish Chesed. Not only does he not do Chesed - even when he is moved by a downtrodden person's affliction, he does not have mercy on him and does not benefit him. Do not think that he troubles his spiritual Nefesh, but he benefits his body. He troubles also She'ero and his body via his cruelty "Ocher Beiso Yinchal Ru'ach" (29; he bequeaths nothing. One who is in the middle between Ish Chesed and Achzari, even though he is not Gomel Nafsho, he does not trouble She'ero.)
