*Club domestic league appearances and goals, correct as of 15 December 2023 ‡ National team caps and goals, correct as of 14:15; 14 November 2024 (UTC)
Kempter, a product of the FC Zürich youth academy, made his league debut for the club on 24 April 2016 in a 3–0 away defeat to Young Boys, coming on as an 81st minute substitute for Vinícius Freitas.[3] He scored his first competitive goal for the club on 10 April 2017 in a 5–2 away victory in the league over Le Mont.[4] His goal, scored in the 54th minute, made the score 5–0 to Zürich.[citation needed]
In June 2017, Kempter suffered a rupture of the cruciate ligament.[5] He was out until March 2018 and only one month later, he got injured again and had to get a surgery. On 1 February 2019, Kempter was relegated to the U-21 squad.[6] In August 2020 his contract was not renewed.[7]
On 18 June 2023, Kempter joined Grasshopper on a free transfer.[13] He signed a two-year deal with the Swiss giants. He started and played the full 90 minutes in the first four games of the season. Sadly, on 27 August 2023, in his fifth start for Grasshoppers he had to be subbed off after a little over 60 minutes with an ACL and meniscus injury, thus ending his season prematurely.[14]
Kempter confirmed his decision to represent the Philippines in 2018, but did not receive his first call-up until June 2019 ahead of a friendly against China[17] as the process to secure eligibility documents delayed the switch.[18] He made his debut on 7 June 2021 in a 2022 FIFA World Cup qualification against China .[19] In the 14th minute, his nose was elbowed in a controversial challenge from Tang Miao, and he had to be taken off the pitch. Tang was not booked for the incident, and a disappointed coach Scott Cooper confronted referee Kim Hee-gon at halftime, who allegedly claimed that Kempter "broke his own nose".[20][21]