3 sentences

1. 他虽然处于劣势，但绝不肯认输。

   tā suī​rán chǔ​yú liè​shì, dàn jué bù kěn rèn​shū.

   Despite being at a disadvantage, he refuses to admit defeat.

   Source: Dong Chinese Dictionary

2. 他最后跳马将军，对方只能认输了。

   tā zuì​hòu tiào​mǎ jiāng​jūn, duì​fāng zhǐ néng rèn​shū le.

   He finally moved his knight to checkmate, forcing his opponent to concede.

   Source: Dong Chinese Dictionary

3. 虽然对方已经认输了，他还是不肯就此罢手。

   suī​rán duì​fāng yǐ​jīng rèn​shū le, tā hái​shi bù kěn jiù​cǐ bà​shǒu.

   Even though the other side had already admitted defeat, he still refused to let the matter rest.

   Source: Dong Chinese Dictionary